Some of the more technical terms about which there might be some doubt, as they are not always accompanied by explanations in the text, are here briefly defined.
Anatomy.—The study of the details and relative arrangements of the internal features of plants; in particular, the relations of the different tissue systems.
Bracts.—Organs of the nature of leaves, though not usual foliage leaves. They often surround fructifications, and are generally brown and scaly, though they may be brightly coloured or merely green.
Calcareous.—Containing earthy carbonates, particularly calcium carbonate (chalk).
Cambium.—Narrow living cells, which are constantly dividing and giving rise to new tissues (seefig. 33,p. 57).
Carbonates, as used in this book, refer to the combinations of some earthy mineral, such as calcium or magnesium, combined with carbonic acid gas and oxygen, formula CaCO3, MgCO3, &c.
Carpel.—The closed structure covering the seeds which grow attached to it. The “husk” of a peapod is a carpel.
Cell.—The unit of a plant body. Fundamentally a mass of living protoplasm with its nucleus, surrounded in most cases by a wall. Mature cells show many varieties of shape and organization. See Chapter VI,p. 54.
Centrifugal.—Wood or other tissues developed away from the centre of the stem. Seefig. 65,p. 97.
Centripetal.—Wood or other tissues developed towards the centre of the stem. Seefig. 65,p. 97.
Chloroplast.—The microscopic coloured masses, usually round, green bodies, in the cells of plants which are actively assimilating.
Coal Balls.—Masses of carbonate of calcium, magnesium, &c., generally of roundish form, which are found embedded in the coal, and contain petrified plant tissues. Seep. 28.
Concretions.—Roundish mineral masses, formed in concentric layers, like the coats of an onion. Seep. 27.
Cotyledons.—The first leaves of an embryo. In many cases packed with food and filling the seed. Seefig. 58.
Cross Fertilization.—The fusion of male and female cells from different plants.
Cuticle.—A skin of a special chemical nature which forms on the outer wall of the epidermis cells. Seep. 54,fig. 21.
Earth Movements.—The gradual shifting of the level of the land, and the bending and contortions of rocks which result from the slow shrinking of the earth’s surface, and give rise to earthquakes and volcanic action.
Embryo.—The very young plant, sometimes consisting of only a few delicate cells, which results from the divisions of the fertilized egg cell. The embryo is an essential part of modern seeds, and often fills the whole seed, as in a bean, where the two fleshy masses filling it are the two first leaves of the embryo. Seefig. 58,p. 77.
Endodermis.—The specialized layer of cells forming a sheath round the vascular tissue. Seep. 55.
Endosperm.—The many-celled tissue which fills the large “spore” in the Gymnosperm seed, into which the embryo finally grows. Seefig. 57.
Epidermis.—Outer layer of cells, which forms a skin, in the multicellular plants. Seefig. 21,p. 54.
Fruit.—Essentially consisting of a seed or seeds, enclosed in some surrounding tissues, which may be only those of the carpel, or may also be other parts of the flower fused to it. Thus a peapod is afruit, containing the peas, which are seeds.
Gannister.—A very hard, gritty rock found below some coal seams. Seep. 25.
Genus.—A small group within a family which includes all the plants very like each other, to which are all given the same “surname”; e.g.Pinus montana,Pinus sylvestris,Pinus Pinaster, &c. &c., are all members of the genusPinus, and would be called “pine trees” in general (see “Species”).
Hyphæ.—The delicate elongated cells of Fungi.
Molecule.—The group of chemical elements, in a definite proportion, which is the basis of any compound substance;e.g.two atoms of hydrogen and one atom of oxygen form a molecule of water, H2O. A lime carbonate molecule (see definition of “Carbonate”) is represented as CaCO3.
Monostelic.—A type of stem that contains only one stele.
Morphology.—The study of the features of plants, their shapes and relations, and the theories regarding the origin of the organs.
Nucellus.—The tissue in a Gymnosperm seed in which the large “spore” develops. See figs.55and56,p. 76.
Nucleus.—The more compact mass of protoplasm in the centre of each living cell, which controls its growth and division. Seefig. 17,n.
Palæobotany.—The study of fossil plants.
Palæontology.—The study of fossil organisms, both plants and animals.
Petiole.—The stalk of a leaf, which attaches it to the stem.
Phloem.—Commonly called “bast”. The elongated vessel-like cells which conduct the manufactured food. Seep. 57.
Pollen Chamber.—The cavity inside a Gymnosperm seed in which the pollen grains rest for some time before giving out the male cells which fertilize the egg-cell in the seed. Seep. 76.
Polystelic.—A type of stem that appears, in any transverse section, to contain several steles. See note on the use of the word onp. 63.
Protoplasm.—The colourless, constantly moving mass of finely granulated, jelly-like substance, which is the essentially living part of both plants and animals.
Rock.—Used by a geologist for all kinds of earth layers. Clay, and even gravel, are “rocks” in a geological sense.
Roof, of a coal seam. The layers of rock—usually shale, limestone, or sandstone—which lie just above the coal. Seep. 24.
Sclerenchyma.—Cells with very thick walls, specially modified for strengthening the tissues. Seefig. 28,p. 56.
Seed.—Essentially consisting of a young embryo and the tissues round it, which are enclosed in a double coat. See definition of “Fruit”.
Shale.—A fine-grained soft rock, formed of dried and pressed mud or silt, which tends to split into thin sheets, on the surface of which fossils are often found.
Species.—Individuals which in all essentials are identical are said to be of the same species. As there are many variations which are not essential, it is sometimes far from easy to draw the boundary between actual species. The specific name comes after that of the genus, e.g.Pinus montanais a species of the genusPinus, as is alsoPinus sylvestris. See “Genus”.
Sporangium.—The saclike case which contains the spores. See figs.52and53,p. 75.
Spore.—A single cell (generally protected by a cell wall) which has the power of germinating and reproducing the plant of which it is the reproductive body. Seep. 75.
Sporophyll.—A leaf or part of a leaf which bears spores or seeds, and which may be much or little modified.
Stele.—A strand of vascular tissue completely enclosed in an endodermis. Seep. 62.
Stigma.—A special protuberance of the carpel in flowering plants which catches the pollen grains.
Stomates.—Breathing pores in the epidermis, which form as a space between two curved liplike cells. Seefig. 23,p. 54.
Tetrads.—Groups of four cells which develop by the division of a single cell called the “mother cell”. Spores and pollen grains are nearly always formed in this way. Seep. 75.
Tracheid.—A cell specially modified for conducting or storing of water, often much elongated. The long wood cells of Ferns and Gymnosperms are tracheids.
Underclay.—The fine clay found immediately below some coal seams. Seep. 24.
Vascular Tissue.—The elongated cells which are specialized for conduction of water and semifluid foodstuffs.
[1]My book was entirely written before the second edition of Scott’sStudiesappeared, which, had it been available, would have tempted me to escape some of the labour several of the chapters of this little book involved.[2]The student would do well to read up the general geology of this very interesting subject. Such books as Lyell’sPrinciples of Geology, Geikie’s textbooks, and many others, provide information about the process of “mountain building” on which the form of our coalfields depends. A good elementary account is to be found in Watt’sGeology for Beginners, p. 96et seq.[3]Seenote on p. 28.[4]This refers only to the “coal-ball”-bearing seams; there are many other coals which have certainly collected in other ways. See Stopes & Watson, Appendix, p. 187.[5]For a detailed list of the strata refer to Watts, p. 219 (see Appendix).[6]Though the Angiosperm was not then evolved, the Gymnosperm stem has distinct vascular bundles arranged as are those of the Angiosperm, the difference here lies in the type of wood cells.[7]The gametophyte generation (represented in the ferns by the prothallium on which the sexual organs develop) alternates with the large, leafy sporophyte. Refer to Scott’s volume onFlowerless Plants(see Appendix) for an account of this alternation of generations.[8]Material recently obtained by the author and Dr. Fujii in Japan does contain some true petrifactions of Angiosperms and other plant debris. The account of these discoveries has not yet been published.[9]A fuller account of the Angiospermic flora can be had in French, in M. Laurent’s paper inProgressus Rei Botanicæ. See Appendix for reference.[10]From the Cretaceous deposits of North America several fossil forms (Brachyphyllum,Protodammara) are described which show clear affinities with the family as it is now constituted. (See Hollick and Jeffrey; reference in the Appendix.)[11]The addition of-oxylonto the generic name of any living type indicates that we are dealing with a fossil which closely resembles the living type so far as we have information from the petrified material.[12]See reference in the Appendix to this richly illustrated volume.[13]For fuller description of this interesting cone, see Scott’sStudies, p. 114et seq.[14]A brackish swampy land is physiologically dry, as the plants cannot use the water. See Warming’sOecology of Plants, English edition, for a detailed account of such conditions. For a simple account see Stopes’The Study of Plant Life, p. 170.[15]The student interested in this special flora should refer to Arber’s British MuseumCatalogue of the Fossil Plants of the Glossopteris Flora.
[1]My book was entirely written before the second edition of Scott’sStudiesappeared, which, had it been available, would have tempted me to escape some of the labour several of the chapters of this little book involved.
[2]The student would do well to read up the general geology of this very interesting subject. Such books as Lyell’sPrinciples of Geology, Geikie’s textbooks, and many others, provide information about the process of “mountain building” on which the form of our coalfields depends. A good elementary account is to be found in Watt’sGeology for Beginners, p. 96et seq.
[3]Seenote on p. 28.
[4]This refers only to the “coal-ball”-bearing seams; there are many other coals which have certainly collected in other ways. See Stopes & Watson, Appendix, p. 187.
[5]For a detailed list of the strata refer to Watts, p. 219 (see Appendix).
[6]Though the Angiosperm was not then evolved, the Gymnosperm stem has distinct vascular bundles arranged as are those of the Angiosperm, the difference here lies in the type of wood cells.
[7]The gametophyte generation (represented in the ferns by the prothallium on which the sexual organs develop) alternates with the large, leafy sporophyte. Refer to Scott’s volume onFlowerless Plants(see Appendix) for an account of this alternation of generations.
[8]Material recently obtained by the author and Dr. Fujii in Japan does contain some true petrifactions of Angiosperms and other plant debris. The account of these discoveries has not yet been published.
[9]A fuller account of the Angiospermic flora can be had in French, in M. Laurent’s paper inProgressus Rei Botanicæ. See Appendix for reference.
[10]From the Cretaceous deposits of North America several fossil forms (Brachyphyllum,Protodammara) are described which show clear affinities with the family as it is now constituted. (See Hollick and Jeffrey; reference in the Appendix.)
[11]The addition of-oxylonto the generic name of any living type indicates that we are dealing with a fossil which closely resembles the living type so far as we have information from the petrified material.
[12]See reference in the Appendix to this richly illustrated volume.
[13]For fuller description of this interesting cone, see Scott’sStudies, p. 114et seq.
[14]A brackish swampy land is physiologically dry, as the plants cannot use the water. See Warming’sOecology of Plants, English edition, for a detailed account of such conditions. For a simple account see Stopes’The Study of Plant Life, p. 170.
[15]The student interested in this special flora should refer to Arber’s British MuseumCatalogue of the Fossil Plants of the Glossopteris Flora.
(Italicized numbers refer to illustrations)