Fig. 48.Fig. 48.—A, young.B, full-grown fruit of a toadstool (Coprinus), × 2.C, under side of the cap, showing the radiating “gills,†or spore-bearing plates.D, section across one of the young gills, × 150.E,F, portions of gills from a nearly ripe fruit, × 300.sp.spores.x, sterile cell. InF, a basidium is shown, with the young spores just forming.G,H, young fruits, × 50.
Fig. 48.—A, young.B, full-grown fruit of a toadstool (Coprinus), × 2.C, under side of the cap, showing the radiating “gills,†or spore-bearing plates.D, section across one of the young gills, × 150.E,F, portions of gills from a nearly ripe fruit, × 300.sp.spores.x, sterile cell. InF, a basidium is shown, with the young spores just forming.G,H, young fruits, × 50.
The first trace of the plant, visible to the naked eye, is a little downy, white speck, just large enough to be seen. This rapidly increases in size, becoming oblong in shape, and growing finally somewhat darker in color; and by the time it reaches a height of a few millimetres a short stalk becomes perceptible, and presently the whole assumes the form of a closed umbrella. The top is covered with little prominences, that diminish in number and size toward the bottom. After the cap reaches its full size, the stalk begins to grow, slowly at first, but finally with great rapidity, reaching a height ofseveral centimetres within a few hours. At the same time that the stalk is elongating, the cap spreads out, radial clefts appearing on its upper surface, which flatten out very much as the folds of an umbrella are stretched as it opens, and the spaces between the clefts appear as ridges, comparable to the ribs of the umbrella (Fig. 48,B). The under side of the cap has a number of ridges running from the centre to the margin, and of a black color, due to the innumerable spores covering their surface (C). Almost as soon as the umbrella opens, the spores are shed, and the whole structure shrivels up and dissolves, leaving almost no trace behind.
Fig. 49.Fig. 49.—Basidiomycetes.A, common puff-ball (Lycoperdon).B, earth star (Geaster).A, × ¼.B, one-half natural size.
Fig. 49.—Basidiomycetes.A, common puff-ball (Lycoperdon).B, earth star (Geaster).A, × ¼.B, one-half natural size.
If we examine microscopically the youngest specimens procurable, freeing from air with alcohol, and mounting in water or dilute glycerine, we find it to be a little, nearly globular mass of colorless filaments, with numerous cross-walls, the whole arising from similar looser filaments imbedded in the substratum (Fig. 48,G). If the specimen is not too young, a denser central portion can be made out, and in still older ones (Fig. 48,H) this central mass has assumed the form of a short, thick stalk, crowned by a flat cap, the whole invested by a loose mass of filaments that merge more or less gradually into the central portion. By the time the spore fruit (for this structure corresponds to the spore fruit of theAscomycetes) reaches a height of two or three millimetres, and is plainly visible to the naked eye, the cap grows downward at the margins, so as to almost entirely conceal the stalk. A longitudinal section of such a stage shows the stalk to be composed of a small-celled, close tissue becoming looser in the cap, on whose inner surface the spore-bearing ridges (“gills†orLamellæ) have begun to develop. Some of these run completely to the edge of the cap, others only part way. To study their structure, make cross-sections of the cap of a nearly full-grown, but unopened, specimen, and this will give numerous sections of the young gills. We find them to be flat plates, composed within of loosely interwoven filaments, whose ends stand out at right angles to the surface of the gills, forming a layer of closely-set upright cells (basidia) (Fig. 48,D). These are at first all alike, but later some of them become club-shaped, and develop at the end several (usually four) little points, at the end of which spores are formed in exactly the same way as we saw in the germinating teleuto spores of the cedar rust, all the protoplasm of the basidium passing into the growing spores (Fig. 48,E,F). The ripe spores (E,sp.) are oval, and possess a firm, dark outer wall. Occasionally some of the basidia develop intovery large sterile cells (E,x), projecting far beyond the others, and often reaching the neighboring gill.
If we examine microscopically the youngest specimens procurable, freeing from air with alcohol, and mounting in water or dilute glycerine, we find it to be a little, nearly globular mass of colorless filaments, with numerous cross-walls, the whole arising from similar looser filaments imbedded in the substratum (Fig. 48,G). If the specimen is not too young, a denser central portion can be made out, and in still older ones (Fig. 48,H) this central mass has assumed the form of a short, thick stalk, crowned by a flat cap, the whole invested by a loose mass of filaments that merge more or less gradually into the central portion. By the time the spore fruit (for this structure corresponds to the spore fruit of theAscomycetes) reaches a height of two or three millimetres, and is plainly visible to the naked eye, the cap grows downward at the margins, so as to almost entirely conceal the stalk. A longitudinal section of such a stage shows the stalk to be composed of a small-celled, close tissue becoming looser in the cap, on whose inner surface the spore-bearing ridges (“gills†orLamellæ) have begun to develop. Some of these run completely to the edge of the cap, others only part way. To study their structure, make cross-sections of the cap of a nearly full-grown, but unopened, specimen, and this will give numerous sections of the young gills. We find them to be flat plates, composed within of loosely interwoven filaments, whose ends stand out at right angles to the surface of the gills, forming a layer of closely-set upright cells (basidia) (Fig. 48,D). These are at first all alike, but later some of them become club-shaped, and develop at the end several (usually four) little points, at the end of which spores are formed in exactly the same way as we saw in the germinating teleuto spores of the cedar rust, all the protoplasm of the basidium passing into the growing spores (Fig. 48,E,F). The ripe spores (E,sp.) are oval, and possess a firm, dark outer wall. Occasionally some of the basidia develop intovery large sterile cells (E,x), projecting far beyond the others, and often reaching the neighboring gill.
Similar in structure and development toCoprinusare all the large and common forms; but they differ much in the position of the spore-bearing tissue, as well as in the form and size of the whole spore fruit. They are sometimes divided, according to the position of the spores, into three orders: the closed-fruited (Angiocarpous) forms, the half-closed (Hemi-angiocarpous), and the open or naked-fruited forms (Gymnocarpous).
Of the first, the puff-balls (Fig. 49) are common examples. One species, the giant puff-ball (Lycoperdon giganteum), often reaches a diameter of thirty to forty centimetres. The earth stars (Geaster) have a double covering to the spore fruit, the outer one splitting at maturity into strips (Fig. 49,B). Another pretty and common form is the little birds’-nest fungus (Cyathus), growing on rotten wood or soil containing much decaying vegetable matter (Fig. 50).
Fig. 50.Fig. 50.—Birds’-nest fungus (Cyathus).A, young.B, full grown.C, section throughB, showing the “sporangia†(sp.). All twice the natural size.
Fig. 50.—Birds’-nest fungus (Cyathus).A, young.B, full grown.C, section throughB, showing the “sporangia†(sp.). All twice the natural size.
In the second order the spores are at first protected, as we have seen inCoprinus, which belongs to this order, but finallybecome exposed. Here belong the toadstools and mushrooms (Fig. 51,B), the large shelf-shaped fungi (Polyporus), so common on tree trunks and rotten logs (Fig. 51,C,D,E), and the prickly fungus (Hydnum) (Fig. 51,G).
Fig. 51.Fig. 51.—Forms ofBasidiomycetes.A,Tremella, one-half natural size.B,Agaricus, natural size.C,E,Polyporus:C, × ½;E, × ¼.D, part of the under surface ofD, natural size.F,Clavaria, a small piece, natural size.G,Hydnum, a piece of the natural size.
Fig. 51.—Forms ofBasidiomycetes.A,Tremella, one-half natural size.B,Agaricus, natural size.C,E,Polyporus:C, × ½;E, × ¼.D, part of the under surface ofD, natural size.F,Clavaria, a small piece, natural size.G,Hydnum, a piece of the natural size.
Of the last, or naked-fruited forms, the commonest belong to the genusClavaria(Fig. 51,F), smooth-branching forms, usually of a brownish color, bearing the spores directly upon the surface of the branches.
TheBryophytes, or mosses, are for the most part land plants, though a few are aquatic, and with very few exceptions are richly supplied with chlorophyll. They are for the most part small plants, few of them being over a few centimetres in height; but, nevertheless, compared with the plants that we have heretofore studied, quite complex in their structure. The lowest members of the group are flattened, creeping plants, or a few of them floating aquatics, without distinct stem and leaves; but the higher ones have a pretty well-developed central axis or stem, with simple leaves attached.
There are two classes—I. Liverworts (Hepaticæ), and II. Mosses (Musci).
One of the commonest of this class, and to be had at any time, is namedMadotheca. It is one of the highest of the class, having distinct stem and leaves. It grows most commonly on the shady side of tree trunks, being most luxuriant near the ground, where the supply of moisture is most constant. It also occurs on stones and rocks in moist places. It closely resembles a true moss in general appearance, and from the scale-like arrangement of its leaves is sometimes called “scale moss.â€
The leaves (Fig. 52,A,B) are rounded in outline unequally, two-lobed, and arranged in two rows on the upper side of the stem, so closely overlapping as to conceal it entirely. On the under side are similar but smaller leaves, less regularly disposed. The stems branch at intervals, the branches spreading out laterally so that the whole plant is decidedly flattened. On the under side are fine, whitish hairs, that fasten it to the substratum. If we examine a number of specimens, especially early in the spring, a difference will be observed in the plants. Some of them will be found to bear peculiar structures (Fig. 52,C,D), in which the spores are produced. These are called “sporogonia.†They are at first globular, but when ripe open by means of four valves, and discharge a greenish brown mass of spores. An examination of the younger parts of the same plants will probably show small buds (Fig. 54,H), which contain the female reproductive organs, from which the sporogonia arise.
Fig. 52.Fig. 52.—A, part of a plant of a leafy liverwort (Madotheca), × 2.B, part of the same, seen from below, × 4.C, a branch with two open sporogonia (sp.), × 4.D, a single sporogonium, × 8.
Fig. 52.—A, part of a plant of a leafy liverwort (Madotheca), × 2.B, part of the same, seen from below, × 4.C, a branch with two open sporogonia (sp.), × 4.D, a single sporogonium, × 8.
On other plants may be found numerous short side branches (Fig. 53,B), with very closely set leaves. If these are carefully separated, the antheridia can just be seen as minute whitish globules, barely visible to the naked eye. Plants that,like this one, have the male and female reproductive organs on distinct plants, are said to be “diÅ“cious.â€
A microscopical examination of the stem and leaves shows their structure to be very simple. The former is cylindrical, and composed of nearly uniform elongated cells, with straight cross-walls. The leaves consist of a single layer of small, roundish cells, which, like those of the stem, contain numerous rounded chloroplasts, to which is due their dark green color.The tissues are developed from a single apical cell, but it is difficult to obtain good sections through it.The antheridia are borne singly at the bases of the leaves on the special branches already described (Fig. 53,A,an.). By carefully dissecting with needles such a branch in a drop of water, some of the antheridia will usually be detached uninjured, and may be readily studied, the full-grown ones being just large enough to be seen with the naked eye. They are globular bodies, attached by a stalk composed of two rows of cells. The globular portion consists of a wall of chlorophyll-bearing cells, composed of two layers below, but single above (Fig. 53,C). Within is a mass of excessively small cells, each of which contains a spermatozoid. In the young antheridium (A,an.) the wall is single throughout, and the central cells few in number. To study them in their natural position, thin longitudinal sections of the antheridial branch should be made.
A microscopical examination of the stem and leaves shows their structure to be very simple. The former is cylindrical, and composed of nearly uniform elongated cells, with straight cross-walls. The leaves consist of a single layer of small, roundish cells, which, like those of the stem, contain numerous rounded chloroplasts, to which is due their dark green color.
The tissues are developed from a single apical cell, but it is difficult to obtain good sections through it.
The antheridia are borne singly at the bases of the leaves on the special branches already described (Fig. 53,A,an.). By carefully dissecting with needles such a branch in a drop of water, some of the antheridia will usually be detached uninjured, and may be readily studied, the full-grown ones being just large enough to be seen with the naked eye. They are globular bodies, attached by a stalk composed of two rows of cells. The globular portion consists of a wall of chlorophyll-bearing cells, composed of two layers below, but single above (Fig. 53,C). Within is a mass of excessively small cells, each of which contains a spermatozoid. In the young antheridium (A,an.) the wall is single throughout, and the central cells few in number. To study them in their natural position, thin longitudinal sections of the antheridial branch should be made.
Fig. 53.Fig. 53.—A, end of a branch from a male plant ofMadotheca. The small side branchlets bear the antheridia, × 2.B, two young antheridia (an.), the upper one seen in optical section, the lower one from without, × 150.C, a ripe antheridium, optical section, × 50.D, sperm cells with young spermatozoids.E, ripe spermatozoids, × 600.
Fig. 53.—A, end of a branch from a male plant ofMadotheca. The small side branchlets bear the antheridia, × 2.B, two young antheridia (an.), the upper one seen in optical section, the lower one from without, × 150.C, a ripe antheridium, optical section, × 50.D, sperm cells with young spermatozoids.E, ripe spermatozoids, × 600.
When ripe, if brought into water, the antheridium bursts at the top intoa number of irregular lobes that curl back and allow the mass of sperm cells to escape. The spermatozoids, which are derived principally from the nucleus of the sperm cells (53,D) are so small as to make a satisfactory examination possible only with very powerful lenses. The ripe spermatozoid is coiled in a flat spiral (53,E), and has two excessively delicate cilia, visible only under the most favorable circumstances.The female organ in the bryophytes is called an “archegonium,†and differs considerably from anything we have yet studied, but recalls somewhat the structure of the oögonium ofChara. They are found in groups, contained in little bud-like branches (54,H). In order to study them, a plant should be chosen that has numbers of such buds, and the smallest that can be found should be used. Those containing the young archegonia are very small; but after one has been fertilized, the leaves enclosing it grow much larger, and the bud becomes quite conspicuous, being surrounded by two or three comparatively large leaves. By dissecting the young buds, archegonia in all stages of growth may be found.
When ripe, if brought into water, the antheridium bursts at the top intoa number of irregular lobes that curl back and allow the mass of sperm cells to escape. The spermatozoids, which are derived principally from the nucleus of the sperm cells (53,D) are so small as to make a satisfactory examination possible only with very powerful lenses. The ripe spermatozoid is coiled in a flat spiral (53,E), and has two excessively delicate cilia, visible only under the most favorable circumstances.
The female organ in the bryophytes is called an “archegonium,†and differs considerably from anything we have yet studied, but recalls somewhat the structure of the oögonium ofChara. They are found in groups, contained in little bud-like branches (54,H). In order to study them, a plant should be chosen that has numbers of such buds, and the smallest that can be found should be used. Those containing the young archegonia are very small; but after one has been fertilized, the leaves enclosing it grow much larger, and the bud becomes quite conspicuous, being surrounded by two or three comparatively large leaves. By dissecting the young buds, archegonia in all stages of growth may be found.
Fig. 54.Fig. 54.—A–D, development of the archegonium ofMadotheca.B, surface view, the others in optical section.o, egg cell, × 150.E, base of a fertilized archegonium, containing a young embryo (em.), × 150.F, margin of one of the leaves surrounding the archegonia.G, young sporogonium still surrounded by the much enlarged base of the archegonium.h, neck of the archegonium.ar.abortive archegonia, × 12.H, short branch containing the young sporogonium, × 4.
Fig. 54.—A–D, development of the archegonium ofMadotheca.B, surface view, the others in optical section.o, egg cell, × 150.E, base of a fertilized archegonium, containing a young embryo (em.), × 150.F, margin of one of the leaves surrounding the archegonia.G, young sporogonium still surrounded by the much enlarged base of the archegonium.h, neck of the archegonium.ar.abortive archegonia, × 12.H, short branch containing the young sporogonium, × 4.
When very young the archegonium is composed of an axial row of three cells, surrounded by a single outer layer of cells, the upper ones forming five or six regular rows, which are somewhat twisted (Fig. 54,A,B). As it becomes older, the lower part enlarges slightly, the whole looking something like a long-necked flask (C,D). The centre of the neck is occupiedby a single row of cells (canal cells), with more granular contents than the outer cells, the lowest cell of the row being somewhat larger than the others (Fig. 54,C,o). When nearly ripe, the division walls of the canal cells are absorbed, and the protoplasm of the lowest cell contracts and forms a globular naked cell, the egg cell (D,o). If a ripe archegonium is placed in water, it soon opens at the top, and the contents of the canal cells are forced out, leaving a clear channel down to the egg cell. If the latter is not fertilized, the inner walls of the neck cells turn brown, and the egg cell dies; but if a spermatozoid penetrates to the egg cell, the latter develops a wall and begins to grow, forming the embryo or young sporogonium.
When very young the archegonium is composed of an axial row of three cells, surrounded by a single outer layer of cells, the upper ones forming five or six regular rows, which are somewhat twisted (Fig. 54,A,B). As it becomes older, the lower part enlarges slightly, the whole looking something like a long-necked flask (C,D). The centre of the neck is occupiedby a single row of cells (canal cells), with more granular contents than the outer cells, the lowest cell of the row being somewhat larger than the others (Fig. 54,C,o). When nearly ripe, the division walls of the canal cells are absorbed, and the protoplasm of the lowest cell contracts and forms a globular naked cell, the egg cell (D,o). If a ripe archegonium is placed in water, it soon opens at the top, and the contents of the canal cells are forced out, leaving a clear channel down to the egg cell. If the latter is not fertilized, the inner walls of the neck cells turn brown, and the egg cell dies; but if a spermatozoid penetrates to the egg cell, the latter develops a wall and begins to grow, forming the embryo or young sporogonium.
Fig. 55.Fig. 55.—Longitudinal section of a nearly full-grown sporogonium ofMadotheca, which has not, however, broken through the overlying cells, × 25.sp.cavity in which the spores are formed.ar.abortive archegonium.
Fig. 55.—Longitudinal section of a nearly full-grown sporogonium ofMadotheca, which has not, however, broken through the overlying cells, × 25.sp.cavity in which the spores are formed.ar.abortive archegonium.
The first division wall to be formed in the embryo is transverse, and is followed by vertical ones (Fig. 54,E,em.). As the embryo enlarges, the walls of the basal part of the archegonium grow rapidly, so that the embryo remains enclosed in the archegonium until it is nearly full-grown (Fig. 55). As it increases in size, it becomes differentiated into three parts: a wedge-shaped base or “foot†penetrating downward into the upper part of the plant, and serving to supply the embryo with nourishment; second, a stalk supporting the third part, the capsule or spore-bearing portion of the fruit. The capsule is further differentiated into a wall, which later becomes dark colored, and a central cavity, in which are developed special cells, some of which by further division into four parts produce the spores, while the others, elongating enormously, give rise to special cells, called elaters (Fig. 56,B).
The first division wall to be formed in the embryo is transverse, and is followed by vertical ones (Fig. 54,E,em.). As the embryo enlarges, the walls of the basal part of the archegonium grow rapidly, so that the embryo remains enclosed in the archegonium until it is nearly full-grown (Fig. 55). As it increases in size, it becomes differentiated into three parts: a wedge-shaped base or “foot†penetrating downward into the upper part of the plant, and serving to supply the embryo with nourishment; second, a stalk supporting the third part, the capsule or spore-bearing portion of the fruit. The capsule is further differentiated into a wall, which later becomes dark colored, and a central cavity, in which are developed special cells, some of which by further division into four parts produce the spores, while the others, elongating enormously, give rise to special cells, called elaters (Fig. 56,B).
Fig. 56.Fig. 56.—Spore (A) and two elaters (B) ofMadotheca, × 300.
Fig. 56.—Spore (A) and two elaters (B) ofMadotheca, × 300.
The ripe spores are nearly globular, contain chlorophyll and drops of oil, and the outer wall is brown and covered with fine points (Fig. 56,A). The elaters are long-pointed cells, having on the inner surface of the wall a single or double dark brown spiral band. These bands are susceptible to changes in moisture, and by their movements probably assist in scattering the spores after the sporogonium opens.
The ripe spores are nearly globular, contain chlorophyll and drops of oil, and the outer wall is brown and covered with fine points (Fig. 56,A). The elaters are long-pointed cells, having on the inner surface of the wall a single or double dark brown spiral band. These bands are susceptible to changes in moisture, and by their movements probably assist in scattering the spores after the sporogonium opens.
Just before the spores are ripe, the stalk of the sporogonium elongates rapidly, carrying up the capsule, which breaks through the archegonium wall, and finally splits into four valves, and discharges the spores.
There are four orders of the liverworts represented in the United States, three of which differ from the one we have studied in being flattened plants, without distinct stems and leaves,—at least, the leaves when present are reduced to little scales upon the lower surface.
The first order (Ricciaceæ) are small aquatic forms, or grow on damp ground or rotten logs. They are not common forms, and not likely to be encountered by the student. One of the floating species is shown infigure 57,A.
The second order, the horned liverworts (Anthoceroteæ), are sometimes to be met with in late summer and autumn, forms growing mostly on damp ground, and at once recognizable by their long-pointed sporogonia, which open when ripe by two valves, like a bean pod (Fig. 57,B).
The third order (Marchantiaceæ) includes the most conspicuous members of the whole class. Some of them, like the common liverwort (Marchantia), shown inFigure 57,F,K, and the giant liverwort (Fig. 57,D), are large and common forms, growing on the ground in shady places, the former being often found also in greenhouses. They are fastened to the ground by numerous fine, silky hairs, and the tissues are well differentiated, the upper surface of the plant having a well-marked epidermis, with peculiar breathing pores, large enough to be seen with the naked eye (Fig. 57,E,J,K) Each of these is situated in the centre of a little area (Fig. 57,E), and beneathit is a large air space, into which the chlorophyll-bearing cells (cl.) of the plant project (J).
The sexual organs are often produced in these forms upon special branches (G), or the antheridia may be sunk in discs on the upper side of the stem (D,an.).
Fig. 57.Fig. 57.—Forms of liverworts.A,Riccia, natural size.B,Anthoceros(horned liverwort), natural size.sp.sporogonia.C,Lunularia, natural size,x, buds.D, giant liverwort (Conocephalus), natural size.an.antheridial disc.E, small piece of the epidermis, showing the breathing pores, × 2.F, common liverwort (Marchantia), × 2.x, cups containing buds.G, archegonial branch of common liverwort, natural size.H, two young buds from the common liverwort, × 150.I, a full-grown bud, × 25.J, vertical section through the body ofMarchantia, cutting through a breathing pore (s), × 50.K, surface view of a breathing pore, × 150.L, a leafy liverwort (Jungermannia).sp.sporogonium, × 2.
Fig. 57.—Forms of liverworts.A,Riccia, natural size.B,Anthoceros(horned liverwort), natural size.sp.sporogonia.C,Lunularia, natural size,x, buds.D, giant liverwort (Conocephalus), natural size.an.antheridial disc.E, small piece of the epidermis, showing the breathing pores, × 2.F, common liverwort (Marchantia), × 2.x, cups containing buds.G, archegonial branch of common liverwort, natural size.H, two young buds from the common liverwort, × 150.I, a full-grown bud, × 25.J, vertical section through the body ofMarchantia, cutting through a breathing pore (s), × 50.K, surface view of a breathing pore, × 150.L, a leafy liverwort (Jungermannia).sp.sporogonium, × 2.
Some forms, likeMarchantiaandLunularia(Fig. 57,C), produce little cups (x), circular in the first, semicircular in the second, in which special buds (H,I) are formed that fall off and produce new plants.
The highest of the liverworts (Jungermanniaceæ) are, forthe most part, leafy forms likeMadotheca, and represented by a great many common forms, growing usually on tree trunks, etc. They are much likeMadothecain general appearance, but usually very small and inconspicuous, so as to be easily overlooked, especially as their color is apt to be brownish, and not unlike that of the bark on which they grow (Fig. 57,L).
The true mosses (Musci) resemble in many respects the higher liverworts, such asMadothecaorJungermannia, all of them having well-marked stems and leaves. The spore fruit is more highly developed than in the liverworts, but never contains elaters.
A good idea of the general structure of the higher mosses may be had from a study of almost any common species. One of the most convenient, as well as common, forms (Funaria) is to be had almost the year round, and fruits at almost all seasons, except midwinter. It grows in close patches on the ground in fields, at the bases of walls, sometimes in the crevices between the bricks of sidewalks, etc. If fruiting, it may be recognized by the nodding capsule on a long stalk, that is often more or less twisted, being sensitive to changes in the moisture of the atmosphere. The plant (Fig. 58,A,B) has a short stem, thickly set with relatively large leaves. These are oblong and pointed, and the centre is traversed by a delicate midrib. The base of the stem is attached to the ground by numerous fine brown hairs.
The mature capsule is broadly oval in form (Fig. 58,C), and provided with a lid that falls off when the spores are ripe. While the capsule is young it is covered by a pointed membranous cap (B,cal.) that finally falls off. When the lid is removed, a fine fringe is seen surrounding the opening of the capsule, and serving the same purpose as the elaters of the liverworts (Fig. 58,E).
Fig. 58.Fig. 58.—A, fruiting plant of a moss (Funaria), with young sporogonium (sp.), × 4. B, plant with ripe sporogonium.cal. calyptra, × 2.C, sporogonium with calyptra removed.op.lid, × 4.D, spores:i, ungerminated;ii–iv, germinating, × 300.E, two teeth from the margin of the capsule, × 50.F, epidermal cells and breathing pore from the surface of the sporogonium, × 150.G, longitudinal section of a young sporogonium, × 12.sp.spore mother cells.H, a small portion ofG, magnified about 300 times.sp.spore mother cells.
Fig. 58.—A, fruiting plant of a moss (Funaria), with young sporogonium (sp.), × 4. B, plant with ripe sporogonium.cal. calyptra, × 2.C, sporogonium with calyptra removed.op.lid, × 4.D, spores:i, ungerminated;ii–iv, germinating, × 300.E, two teeth from the margin of the capsule, × 50.F, epidermal cells and breathing pore from the surface of the sporogonium, × 150.G, longitudinal section of a young sporogonium, × 12.sp.spore mother cells.H, a small portion ofG, magnified about 300 times.sp.spore mother cells.
If the lower part of the stem is carefully examined with a lens, we may detect a number of fine green filaments growing from it, looking like the root hairs, except for their color. Sometimes the ground about young patches of the moss is quite covered by a fine film of such threads, and looking carefully over it probably very small moss plants may be seen growing up here and there from it.
Fig. 59.Fig. 59.—Longitudinal section through the summit of a small male plant ofFunaria.a,aʹ, antheridia.p, paraphysis.L, section of a leaf, × 150.
Fig. 59.—Longitudinal section through the summit of a small male plant ofFunaria.a,aʹ, antheridia.p, paraphysis.L, section of a leaf, × 150.
This moss is diœcious. The male plants are smaller than the female, and may be recognized by the bright red antheridia which are formed at the end of the stem in considerable numbers, and surrounded by a circle of leaves so that the wholelooks something like a flower. (This is still more evident in some other mosses. SeeFigure 65,E,F.)
The leaves when magnified are seen to be composed of a single layer of cells, except the midrib, which is made up of several thicknesses of elongated cells. Where the leaf is one cell thick, the cells are oblong in form, becoming narrower as they approach the midrib and the margin. They contain numerous chloroplasts imbedded in the layer of protoplasm that lines the wall. The nucleus (Fig. 63,C,n) may usually be seen without difficulty, especially if the leaf is treated with iodine. This plant is one of the best for studying the division of the chloroplasts, which may usually be found in all stages of division (Fig. 63,D). In the chloroplasts, especially if the plant has been exposed to light for several hours, will be found numerous small granules, that assume a bluish tint on the application of iodine, showing them to be starch grains. If the plant is kept in the dark for a day or two, these will be absent, having been used up; but if exposed to the light again, new ones will be formed, showing that they are formed only under the action of light.
The leaves when magnified are seen to be composed of a single layer of cells, except the midrib, which is made up of several thicknesses of elongated cells. Where the leaf is one cell thick, the cells are oblong in form, becoming narrower as they approach the midrib and the margin. They contain numerous chloroplasts imbedded in the layer of protoplasm that lines the wall. The nucleus (Fig. 63,C,n) may usually be seen without difficulty, especially if the leaf is treated with iodine. This plant is one of the best for studying the division of the chloroplasts, which may usually be found in all stages of division (Fig. 63,D). In the chloroplasts, especially if the plant has been exposed to light for several hours, will be found numerous small granules, that assume a bluish tint on the application of iodine, showing them to be starch grains. If the plant is kept in the dark for a day or two, these will be absent, having been used up; but if exposed to the light again, new ones will be formed, showing that they are formed only under the action of light.
Fig. 60.Fig. 60.—A,B, young antheridia ofFunaria, optical section, × 150.C, two sperm cells ofAtrichum.D, spermatozoids ofSphagnum, × 600.
Fig. 60.—A,B, young antheridia ofFunaria, optical section, × 150.C, two sperm cells ofAtrichum.D, spermatozoids ofSphagnum, × 600.
Starch is composed of carbon, hydrogen, and oxygen, and so far as is known is only produced by chlorophyll-bearing cells, under the influence of light. The carbon used in the manufacture of starch is taken from the atmosphere in the form of carbonic acid, so that green plants serve to purify the atmosphere by the removal of this substance, which is deleterious to animal life, while at the same time the carbon, an essential part of all livingmatter, is combined in such form as to make it available for the food of other organisms.The marginal cells of the leaf are narrow, and some of them prolonged into teeth.A cross-section of the stem (63,E) shows on the outside a single row of epidermal cells, then larger chlorophyll-bearing cells, and in the centre a group of very delicate, small, colorless cells, which in longitudinal section are seen to be elongated, and similar to those forming the midrib of the leaf. These cells probably serve for conducting fluids, much as the similar but more perfectly developed bundles of cells (fibro-vascular bundles) found in the stems and leaves of the higher plants.The root hairs, fastening the plant to the ground, are rows of cells with brown walls and oblique partitions. They often merge insensibly into the green filaments (protonema) already noticed. These latter have usually colorless walls, and more numerous chloroplasts, looking very much like a delicate specimen ofCladophoraor some similar alga. If a sufficient number of these filaments is examined, some of them will probably show young moss plants growing from them (Fig. 63,A,k), and with a little patience the leafy plant can be traced back to a little bud originating as a branch of the filament. Its diameter is at first scarcely greater than that of the filament, but a series of walls, close together, are formed, so placed as to cut off a pyramidal cell at the top, forming the apical cell of the young moss plant. This apical cell has the form of a three-sided pyramid with the base upward. From it are developed three series of cells, cut off in succession from the three sides, and from these cells are derived all the tissues of the plant which soon becomes of sufficient size to be easily recognizable.The protonemal filaments may be made to grow from almost any part of the plant by keeping it moist, but grow most abundantly from the base of the stem.The sexual organs are much like those of the liverworts and are borne at the apex of the stems.The antheridia (Figs.59,60) are club-shaped bodies with a short stalk. The upper part consists of a single layer of large chlorophyll-bearing cells, enclosing a mass of very small, nearly cubical, colorless, sperm cells each of which contains an excessively small spermatozoid.The young antheridium has an apical cell giving rise to two series of segments (Fig. 60,A), which in the earlier stages are very plainly marked.When ripe the chlorophyll in the outer cells changes color, becoming red, and if a few such antheridia from a plant that has been kept rather dry for a day or two, are teased out in a drop of water, they will quicklyopen at the apex, the whole mass of sperm cells being discharged at once.Among the antheridia are borne peculiar hairs (Fig. 59,p) tipped by a large globular cell.
Starch is composed of carbon, hydrogen, and oxygen, and so far as is known is only produced by chlorophyll-bearing cells, under the influence of light. The carbon used in the manufacture of starch is taken from the atmosphere in the form of carbonic acid, so that green plants serve to purify the atmosphere by the removal of this substance, which is deleterious to animal life, while at the same time the carbon, an essential part of all livingmatter, is combined in such form as to make it available for the food of other organisms.
The marginal cells of the leaf are narrow, and some of them prolonged into teeth.
A cross-section of the stem (63,E) shows on the outside a single row of epidermal cells, then larger chlorophyll-bearing cells, and in the centre a group of very delicate, small, colorless cells, which in longitudinal section are seen to be elongated, and similar to those forming the midrib of the leaf. These cells probably serve for conducting fluids, much as the similar but more perfectly developed bundles of cells (fibro-vascular bundles) found in the stems and leaves of the higher plants.
The root hairs, fastening the plant to the ground, are rows of cells with brown walls and oblique partitions. They often merge insensibly into the green filaments (protonema) already noticed. These latter have usually colorless walls, and more numerous chloroplasts, looking very much like a delicate specimen ofCladophoraor some similar alga. If a sufficient number of these filaments is examined, some of them will probably show young moss plants growing from them (Fig. 63,A,k), and with a little patience the leafy plant can be traced back to a little bud originating as a branch of the filament. Its diameter is at first scarcely greater than that of the filament, but a series of walls, close together, are formed, so placed as to cut off a pyramidal cell at the top, forming the apical cell of the young moss plant. This apical cell has the form of a three-sided pyramid with the base upward. From it are developed three series of cells, cut off in succession from the three sides, and from these cells are derived all the tissues of the plant which soon becomes of sufficient size to be easily recognizable.
The protonemal filaments may be made to grow from almost any part of the plant by keeping it moist, but grow most abundantly from the base of the stem.
The sexual organs are much like those of the liverworts and are borne at the apex of the stems.
The antheridia (Figs.59,60) are club-shaped bodies with a short stalk. The upper part consists of a single layer of large chlorophyll-bearing cells, enclosing a mass of very small, nearly cubical, colorless, sperm cells each of which contains an excessively small spermatozoid.
The young antheridium has an apical cell giving rise to two series of segments (Fig. 60,A), which in the earlier stages are very plainly marked.
When ripe the chlorophyll in the outer cells changes color, becoming red, and if a few such antheridia from a plant that has been kept rather dry for a day or two, are teased out in a drop of water, they will quicklyopen at the apex, the whole mass of sperm cells being discharged at once.
Among the antheridia are borne peculiar hairs (Fig. 59,p) tipped by a large globular cell.
Fig. 61.Fig. 61.—A,B, young;C, nearly ripe archegonium ofFunaria, optical section, × 150.D, upper part of the neck ofC, seen from without, showing how it is twisted.E, base of a ripe archegonium.F, open apex of the same, × 150.o, egg cell.b, ventral canal cell.
Fig. 61.—A,B, young;C, nearly ripe archegonium ofFunaria, optical section, × 150.D, upper part of the neck ofC, seen from without, showing how it is twisted.E, base of a ripe archegonium.F, open apex of the same, × 150.o, egg cell.b, ventral canal cell.
Owing to their small size the spermatozoids are difficult to see satisfactorily and other mosses (e.g.peat mosses,Figure 64, the hairy cap moss,Figure 65,I), are preferable where obtainable. The spermatozoids of a peat moss are shown inFigure 60,D. Like all of the bryophytes they have but two cilia.The archegonia (Fig. 61) should be looked for in the younger plants in the neighborhood of those that bear capsules. Like the antheridia they occur in groups. They closely resemble those of the liverworts, but the neck is longer and twisted and the base more massive. Usually but a single one of the group is fertilized.
Owing to their small size the spermatozoids are difficult to see satisfactorily and other mosses (e.g.peat mosses,Figure 64, the hairy cap moss,Figure 65,I), are preferable where obtainable. The spermatozoids of a peat moss are shown inFigure 60,D. Like all of the bryophytes they have but two cilia.
The archegonia (Fig. 61) should be looked for in the younger plants in the neighborhood of those that bear capsules. Like the antheridia they occur in groups. They closely resemble those of the liverworts, but the neck is longer and twisted and the base more massive. Usually but a single one of the group is fertilized.
Fig. 62.Fig. 62.—A, young embryo ofFunaria, still enclosed within the base of the archegonium, × 300.B, an older embryo freed from the archegonium, × 150.a, the apical cell.
Fig. 62.—A, young embryo ofFunaria, still enclosed within the base of the archegonium, × 300.B, an older embryo freed from the archegonium, × 150.a, the apical cell.
To study the first division of the embryo, it is usually necessary to render the archegonium transparent, which may be done by using a little caustic potash; or letting it lie for a few hours in dilute glycerine will sometimes suffice. If potash is used it must be thoroughly washed away, by drawing pure water under the cover glass with a bit of blotting paper,until every trace of the potash is removed. The first wall in the embryo is nearly at right angles to the axis of the archegonium and divides the egg cell into nearly equal parts. This is followed by nearly vertical walls in each cell (Fig. 62,A). Very soon a two-sided apical cell (Fig. 62,B,a) is formed in the upper half of the embryo, which persists until the embryo has reached a considerable size. As in the liverworts the young embryo is completely covered by the growing archegonium wall.The embryo may be readily removed from the archegonium by adding a little potash to the water in which it is lying, allowing it to remain for a few moments and pressing gently upon the cover glass with a needle. In this way it can be easily forced out of the archegonium, and then by thoroughly washing away the potash, neutralizing if necessary with a little acetic acid, very beautiful preparations may be made. If desired, these may be mounted permanently in glycerine which, however, must be added very gradually to avoid shrinking the cells.
To study the first division of the embryo, it is usually necessary to render the archegonium transparent, which may be done by using a little caustic potash; or letting it lie for a few hours in dilute glycerine will sometimes suffice. If potash is used it must be thoroughly washed away, by drawing pure water under the cover glass with a bit of blotting paper,until every trace of the potash is removed. The first wall in the embryo is nearly at right angles to the axis of the archegonium and divides the egg cell into nearly equal parts. This is followed by nearly vertical walls in each cell (Fig. 62,A). Very soon a two-sided apical cell (Fig. 62,B,a) is formed in the upper half of the embryo, which persists until the embryo has reached a considerable size. As in the liverworts the young embryo is completely covered by the growing archegonium wall.
The embryo may be readily removed from the archegonium by adding a little potash to the water in which it is lying, allowing it to remain for a few moments and pressing gently upon the cover glass with a needle. In this way it can be easily forced out of the archegonium, and then by thoroughly washing away the potash, neutralizing if necessary with a little acetic acid, very beautiful preparations may be made. If desired, these may be mounted permanently in glycerine which, however, must be added very gradually to avoid shrinking the cells.
Fig. 63.Fig. 63.—A, protonema ofFunaria, with a bud (k), × 50.B, outline of a leaf, showing also the thickened midrib, × 12.C, cells of the leaf, × 300.n, nucleus.D, chlorophyll granules undergoing division, × 300.E, cross-section of the stem, × 50.
Fig. 63.—A, protonema ofFunaria, with a bud (k), × 50.B, outline of a leaf, showing also the thickened midrib, × 12.C, cells of the leaf, × 300.n, nucleus.D, chlorophyll granules undergoing division, × 300.E, cross-section of the stem, × 50.
For some time the embryo has a nearly cylindrical form, but as it approaches maturity the differentiation into stalk and capsule becomes apparent. The latter increases rapidly in diameter, assuming gradually the oval shape of the full-grown capsule. A longitudinal section of the nearly ripe capsule (Fig. 58,G) shows two distinct portions; an outer wall of two layers of cells, and an inner mass of cells in some of which the spores are produced. This inner mass of cells is continuous with the upper part of the capsule, but connected with the side walls and bottom by means of slender, branching filaments of chlorophyll-bearing cells.The spores arise from a single layer of cells near the outside of the inner mass of cells (G,sp.). These cells (H,sp.) are filled with glistening, granular protoplasm; have a large and distinct nucleus, and nochlorophyll. They finally become entirely separated and each one gives rise to four spores which closely resemble those of the liverworts but are smaller.Near the base of the capsule, on the outside, are formed breathing pores (Fig. 58,F) quite similar to those of the higher plants.If the spores are kept in water for a few days they will germinate, bursting the outer brown coat, and the contents protruding through the opening surrounded by the colorless inner spore membrane. The protuberance grows rapidly in length and soon becomes separated from the body of the spore by a wall, and lengthening, more and more, gives rise to a green filament like those we found attached to the base of the full-grown plant, and like those giving rise to buds that develop into leafy plants.
For some time the embryo has a nearly cylindrical form, but as it approaches maturity the differentiation into stalk and capsule becomes apparent. The latter increases rapidly in diameter, assuming gradually the oval shape of the full-grown capsule. A longitudinal section of the nearly ripe capsule (Fig. 58,G) shows two distinct portions; an outer wall of two layers of cells, and an inner mass of cells in some of which the spores are produced. This inner mass of cells is continuous with the upper part of the capsule, but connected with the side walls and bottom by means of slender, branching filaments of chlorophyll-bearing cells.
The spores arise from a single layer of cells near the outside of the inner mass of cells (G,sp.). These cells (H,sp.) are filled with glistening, granular protoplasm; have a large and distinct nucleus, and nochlorophyll. They finally become entirely separated and each one gives rise to four spores which closely resemble those of the liverworts but are smaller.
Near the base of the capsule, on the outside, are formed breathing pores (Fig. 58,F) quite similar to those of the higher plants.
If the spores are kept in water for a few days they will germinate, bursting the outer brown coat, and the contents protruding through the opening surrounded by the colorless inner spore membrane. The protuberance grows rapidly in length and soon becomes separated from the body of the spore by a wall, and lengthening, more and more, gives rise to a green filament like those we found attached to the base of the full-grown plant, and like those giving rise to buds that develop into leafy plants.
The mosses may be divided into four orders: I. The peat mosses (Sphagnaceæ); II.Andreæaceæ; III.Phascaceæ; IV. The common mosses (Bryaceæ).
Fig. 64.Fig. 64.—A, a peat moss (Sphagnum), × ½.B, a sporogonium of the same, × 3.C, a portion of a leaf, × 150. The narrow, chlorophyll-bearing cells form meshes, enclosing the large, colorless empty cells, whose walls are marked with thickened bars, and contain round openings (o).
Fig. 64.—A, a peat moss (Sphagnum), × ½.B, a sporogonium of the same, × 3.C, a portion of a leaf, × 150. The narrow, chlorophyll-bearing cells form meshes, enclosing the large, colorless empty cells, whose walls are marked with thickened bars, and contain round openings (o).
The peat mosses (Fig. 64) are large pale-green mosses, growing often in enormous masses, forming the foundation of peat-bogs. They are of a peculiar spongy texture, very light when dry, and capable of absorbing a great amount of water. They branch (Fig. 64,A), the branches being closely crowdedat the top, where the stems continue to grow, dying away below.
Fig. 65.Fig. 65.—Forms of mosses.A, plant ofPhascum, × 3.B, fruiting plant ofAtrichum, × 2.C, young capsule of hairy-cap moss (Polytrichum), covered by the large, hairy calyptra.D, capsules ofBartramia: i, with; ii, without the calyptra.E, upper part of a male plant ofAtrichum, showing the flower, × 2.F, a male plant ofMnium, × 4.G, pine-tree moss (Clemacium), × 1.H,Hypnum, × 1.I, ripe capsules of hairy-cap moss:i, with;ii, without calyptra.
Fig. 65.—Forms of mosses.A, plant ofPhascum, × 3.B, fruiting plant ofAtrichum, × 2.C, young capsule of hairy-cap moss (Polytrichum), covered by the large, hairy calyptra.D, capsules ofBartramia: i, with; ii, without the calyptra.E, upper part of a male plant ofAtrichum, showing the flower, × 2.F, a male plant ofMnium, × 4.G, pine-tree moss (Clemacium), × 1.H,Hypnum, × 1.I, ripe capsules of hairy-cap moss:i, with;ii, without calyptra.
The sexual organs are rarely met with, but should be looked for late in autumn or early spring. The antheridial branches are often bright-colored, red or yellow, so as to be very conspicuous. The capsules, which are not often found, are larger than in most of the common mosses, and quite destitute of a stalk, the apparent stalk being a prolongation of the axis of the plant in the top of which the base of the sporogonium is imbedded. The capsule is nearly globular, opening by a lid at the top (Fig. 64,B).
A microscopical examination of the leaves, which are quite destitute of a midrib, shows them to be composed of a network of narrow chlorophyll-bearing cells surrounding much larger empty ones whose walls are marked with transverse thickenings, and perforated here and there with large, round holes (Fig. 64,C). It is to the presence of these empty cells that the plant owes its peculiar spongy texture, the growing plants being fairly saturated with water.
A microscopical examination of the leaves, which are quite destitute of a midrib, shows them to be composed of a network of narrow chlorophyll-bearing cells surrounding much larger empty ones whose walls are marked with transverse thickenings, and perforated here and there with large, round holes (Fig. 64,C). It is to the presence of these empty cells that the plant owes its peculiar spongy texture, the growing plants being fairly saturated with water.
TheAndreæaceæare very small, and not at all common. The capsule splits into four valves, something like a liverwort.
ThePhascaceæare small mosses growing on the ground or low down on the trunks of trees, etc. They differ principally from the common mosses in having the capsule open irregularly and not by a lid. The commonest forms belong to the genusPhascum(Fig. 65,A).
The vast majority of the mosses the student is likely to meet with belong to the last order, and agree in the main with the one described. Some of the commoner forms are shown inFigure 65.
Ifwe compare the structure of the sporogonium of a moss or liverwort with the plant bearing the sexual organs, we find that its tissues are better differentiated, and that it is on the whole a more complex structure than the plant that bears it. It, however, remains attached to the parent plant, deriving its nourishment in part through the “foot†by means of which it is attached to the plant.
In the Pteridophytes, however, we find that the sporogonium becomes very much more developed, and finally becomes entirely detached from the sexual plant, developing in most cases roots that fasten it to the ground, after which it may live for many years, and reach a very large size.
The sexual plant, which is here called the “prothallium,†is of very simple structure, resembling the lower liverworts usually, and never reaches more than about a centimetre in diameter, and is often much smaller than this.
The common ferns are the types of the sub-kingdom, and a careful study of any of these will illustrate the principal peculiarities of the group. The whole plant, as we know it, is really nothing but the sporogonium, originating from the egg cell in exactly the same way as the moss sporogonium, and like it gives rise to spores which are formed upon the leaves.
The spores may be collected by placing the spore-bearing leaves on sheets of paper and letting them dry, when the ripespores will be discharged covering the paper as a fine, brown powder. If these are sown on fine, rather closely packed earth, and kept moist and covered with glass so as to prevent evaporation, within a week or two a fine, green, moss-like growth will make its appearance, and by the end of five or six weeks, if the weather is warm, little, flat, heart-shaped plants of a dark-green color may be seen. These look like small liverworts, and are the sexual plants (prothallia) of our ferns (Fig. 66,F). Removing one of these carefully, we find on the lower side numerous fine hairs like those on the lowersurface of the liverworts, which fasten it firmly to the ground. By and by, if our culture has been successful, we may find attached to some of the larger of these, little fern plants growing from the under side of the prothallia, and attached to the ground by a delicate root. As the little plant becomes larger the prothallium dies, leaving it attached to the ground as an independent plant, which after a time bears the spores.