General Principles
Following the most convenient and at the same time the most logical course, the articleBotany(Vol. 4, p. 299) gives a key to the treatment of the whole subject in the Britannica. This is by A. B. Rendle, keeper of the Department of Botany, British Museum, who acted as general adviser to the editor in the arrangement of this branch of biology in the Britannica. The main article on the subject is under the headingPlants(Vol. 21, p. 728), by a number of eminent authorities. The article is divided as follows:Classification, by A. B. Rendle;Anatomy and History and Bibliography, by A. G. Tansley, lecturer in botany in the University of Cambridge;Physiology, by J. R. Green, formerly lecturer on plant physiology, University of Liverpool;Pathology, by H. M. Ward, formerly professor of botany, University of Cambridge;Ecology, which comprises the study of the relations of the individual plant, or species, or the plant community, with its habitat, by C. E. Moss, curator of the Cambridge University Herbarium;Cytology, which treats of the cell structure of plant organisms, by H. W. T. Wager, president of the Botanical section of the British Association, 1905;Morphology, by S. H. Vines, professor of botany, University of Oxford, and presidentof the Linnean Society, 1900–1904;Distribution, by Sir W. T. Thiselton-Dyer, director of the Kew Botanical Gardens. Supplementary to the articlePlantsare the following, which should all be read carefully:Root(Vol. 23, p. 712),Stem(Vol. 25, p. 875),Leaf(Vol. 16, p. 322),Flower(Vol. 10, p. 553),Fruit(Vol. 11, p. 254). A very important article is that onPalaeobotany(Vol. 20, p. 524), which treats of the distribution, etc., of plant life in prehistoric periods. The contributor is Clement Reid of the Geological Survey of England and Wales, an original investigator in this important field. The advances in the study of minute plant organisms in the past few years have been very great and they receive treatment in the brilliant articleBacteriology(Vol. 3, p. 156), by Prof. H. M. Ward of Cambridge University, and V. H. Blackmann, professor of botany in the University of Leeds.
Other articles in the Britannica which refer to the general principles of the science will be found enumerated at the end of this chapter.
Divisions and Classification
The student must, of course, make himself familiar with the primary divisions of the vegetable kingdom. These are considered in order below. By far the biggest and the most important is that of the Angiosperms. They will be treated first.
Angiosperms: Dicotyledons
The divisionAngiosperms(Vol. 2, p. 9) includes all those flowering plants whose seeds are enclosed in capsules. This division is again divided into two classes: the Dicotyledons (Vol. 8, p. 185), which are distinguished by the presence of a pair of seed-leaves or cotyledons in the embryo contained in the seed; and the Monocotyledons (see Vol. 2, p. 13), which contain only one. The former embraces most of the flowerbearing plants, and includes the following families:—Boraginaceae(Vol. 4, p. 242) to which order belongs such plants as forget-me-nots, borage, heliotrope, etc.Caprifoliaceae(Vol. 5, p. 290), which include elder, honeysuckle, etc.Caryophyllaceae(Vol. 5, p. 439), with the pinks, carnations, etc.Compositae(Vol. 6, p. 811), which is the largest order in this division and includes one-tenth of the whole number of flowering plants, with such varieties as lettuce, dandelion, artichoke, sunflower, chrysanthemum, etc.Convolvulaceae(Vol. 7, p. 67), among which are the convolvulus, sweet potato, bindweed.Crassulaceae(Vol. 7, p. 380), which include a quantity of African plants.Cruciferae(Vol. 7, p. 521), with the wallflower, stock, mustard, cabbage, radish, nasturtium, etc.Cucurbitaceae(Vol. 7, p. 611), among which are the cucumber, melon, etc.Cupuliferae(Vol. 7, p. 635), with the hazel, oak, beech, alder.Ericaceae(Vol. 9, p. 739), with the rhododendron, arbutus, whortleberry, heather.Euphorbiaceae(Vol. 9, p. 892), which include the castor-oil plant, box, euphorbia, etc.Gentianaceae(Vol. 11, p. 601), with the gentian, yellow-wort, bog-bean, etc.Geraniaceae(Vol. 11, p. 762), whose name is derived from the geranium.Labiatae(Vol. 16, p. 3), with peppermint, marjoram, thyme, sage, ground-ivy.Leguminosae(Vol. 16, p. 381), which embrace gorse, furze, scarlet runner, mimosa, acacia, rest-harrow, etc.Malvaceae(Vol. 17, p. 517), with the mallow, hibiscus, hollyhock. TheMoraceae(Vol. 18, p. 814), with the fig, mulberry, banyan, etc.Onagraceae(Vol. 20, p. 104), including the evening primrose, fuschia, etc.Polygonaceae(Vol. 22, p. 26), with dock, rhubarb, buckwheat, etc.Primulaceae(Vol. 22, p. 341), including primrose, cowslip, pimpernel.Ranunculaceae(Vol. 22, p. 895), with the varieties buttercup, clematis, aconite, larkspur, columbine, marsh marigold, anemone.Rosaceae(Vol. 23, p. 722), to which the rose gives the name, and whichinclude strawberry, raspberry, apple, pear, plum, spiraea, blackthorn, etc.Rubiaceae(Vol. 23, p. 808), with gardenias, chincona, coffee, madder.Saxifragaceae(Vol. 24, p. 263), saxifrage, japonica, gooseberry, hydrangea.Scrophulariaceae(Vol. 24, p. 485), with veronica, foxglove, snapdragon, etc.Solanaceae(Vol. 25, p. 356), which embrace henbane, tobacco, deadly nightshade, cape gooseberry, capsicum.Umbelliferae(Vol. 27, p. 575), to which belong ivy, carrot, hemlock, celery, caraway, parsley.Urticaceae(Vol. 27, p. 805), which include the nettle tribes.
Angiosperms: Monocotyledons
The Monocotyledons include theAlismaceae(Vol. 1, p. 671), to which belong the arrow-head, the water plantain, the butomus (so called because the leaves cut the tongues of oxen feeding on them), and other water plants.Aroideae(Vol. 2, p. 640), so called from the Arum family. TheBromeliaceae(Vol. 4, p. 632), including pineapple, Spanish-moss.Cyperaceae(Vol. 7, p. 692), with bulrush, cotton grass, etc.Grasses(Vol. 12, p. 369), a most valuable article.Hydrocharideae(Vol. 14, p. 112), which include a number of water plants. Iridaceae (Vol. 14, p. 793), which include besides the iris, the crocus, gladiolus, etc. TheJuncaceae(Vol. 15, p. 555), or Rush family; and theLiliaceae(Vol. 16, p. 683), which include asparagus, hyacinth, star of Bethlehem, fritillary, bluebell, etc.
Other Divisions
Another big division is that of theGymnosperms(Vol. 12, p. 754). These have naked seed pods; that is to say, the seeds are not enclosed in capsules. The best known and largest division of this class contains the conifers: pines, firs, cedars, larches, etc.
Pteridophyta(Vol. 22, p. 605), or spore-producing plants, including the fern families as the largest and most important of its members.
Bryophyta(Vol. 4, p. 700), the second great sub-division of the vegetable kingdom, comprises the mosses and liverworts.
Algae(Vol. 1, p. 585), plants usually devoid of differentiation into roots, stem, and leaf, coming under the general class of Bryophyta, and including sea-weeds as the main group.
Lichens(Vol. 16, p. 578), compound dual organisms, part algae and part fungus, interesting because the dual organism enables the plant to live where neither of its compounds could live alone. Iceland moss, valuable both for its nutritive and medicinal qualities, comes under this division.
Fungi(Vol. 11, p. 333), an enormous class, comprising, according to Saccardo, 32,000 different species.
Bacteria (seeBacteriology, Vol. 3, p. 156), minute organisms, also known as microbes, bacilli, etc., technically called Schizomycetes.
Insectivorous Plants(Vol. 14, p. 644), more correctly termed Carnivorous, belong to a number of distinct natural orders, but agree in the extraordinary habit of adding to the supplies of nitrogenous material offered them by the soil and atmosphere by the capture and consumption of insects and other small animals.
These are the main divisions, and from the articles describing them the student will acquire a sound knowledge of the characteristics which distinguish each. As a matter of fact, interest in botany as a subject is first inspired by the particular rather than the general—that is to say, the love of individual flowers leads to the study of their habits and life history, thence to a comparison which leads to the recognition of similar characteristics in plants having apparently widely different functions, so that the following section of the subject, touching the natural history of plants, though really placed last in a logical course of reading in botany, will contain much that is alreadyknown to the student who wishes to pursue the subject systematically.
Natural History
In the Britannica from the various articles concerning the natural history of individual plants it is easy to trace back to what family and main division each plant belongs. To the student beginning the subject it will be most suggestive to look up the accounts of the plants which are cultivated in his garden, or which he can find near his home, and find out the family relationship between subjects which appear to differ very widely both in habits and characteristics. From the outline given above in the paragraph devoted to systematic botany an indication will be given him of the surprises which are in store for him as he pursues his investigation. He would not at first suspect, for example, that asparagus and hyacinths were cousins, that roses, apples, and blackthorn are closely related, or that chrysanthemums and artichokes have any connection with one another, let alone cabbage and wallflowers. An excellent scheme to arouse the interest of the young student would therefore be to encourage him to pick out from the list below the names of plants with which he is familiar and of which he can get specimens, and thence work backward until the meanings of the main divisions of the vegetable kingdom are clear to him.
In the natural history section of the following list will be found in alphabetical order the plants which have separate articles in the Britannica. Many plants besides these are of course described. They will be found in the Index, where the volume and page on which a description will be found are given.
CLASSIFIED LIST OF ARTICLES IN THE BRITANNICA ON BOTANY
(For biographies of botanists, see the end of the chapter on Biology)
(For biographies of botanists, see the end of the chapter on Biology)
(For biographies of botanists, see the end of the chapter on Biology)
Botany: General
Botany: Natural History
At the very outset of his zoological studies the reader will find that the doctors still differ as to the best and most scientifically logical system to be employed in classification. So important is it that the connotation and denotation of every zoological designation should be definite, that Sir Edwin Ray Lankester devotes the title articleZoology(Vol. 28, p. 1022) mainly to a discussion of systems of classification, and besides there is a separate articleZoological Nomenclature(Vol. 28, p. 1021) by P. Chalmers Mitchell, Secretary of the Zoological Society of London, university demonstrator in comparative anatomy and assistant to the Linacre Professor at Oxford, and adviser to the editor in the organization of the whole subject of zoology in the Britannica.
The Britannica articles may be classified in three divisions: dealing with (i)General Principles, (ii)Systematic, (iii)Natural History.
General Principles
The student should read at any rate some of the general articles mentioned in the chapter onBiology; and these will prepare him for the difficult questions involved in the articlesZoologyandZoological Nomenclature. Supplementary to these are the following:Animal(Vol. 2, p. 48), in connection with which should be read the articleProtista(Vol. 22, p. 476) where the borderland between the animal and vegetable kingdoms is further discussed, and the very valuable articleProtozoa(Vol. 22, p. 479) in which E. A. Minchin, professor of protozoology in the University of London, discusses the minute animal organisms, which in the last decade have proved immensely important in the study of parasitic diseases. InLarval Forms(Vol. 16, p. 224), andMetamorphosis(Vol. 18, p. 221) Prof. Adam Sedgwick, of the Imperial College of Science and Technology in London, discusses the early history of larvae and their change from larval to adult growth. The articlesMetamerism(Vol. 18, p. 215), by Sir Edwin Ray Lankester, andRegeneration of Lost Parts(Vol. 23, p. 36), by P. Chalmers Mitchell, discuss the capacity for repeating parts (as in the case of the common earth worm) and for the formation of new parts to take the place of those lost by accident or injury. The articleMonster(Vol. 18, p. 740) by Dr. Charles Creighton will be found very suggestive.
Protective Modifications
The eyes of most of us are shut to the wonders of the animal kingdom. We know by hearsay that the colouringof an animal or insect, brilliant and startling though it often be, is designed by nature for protection by enabling it to assimilate itself to that of its surroundings. But how many of us have taken the trouble to verify this? The articlesColours of Animals,Bionomics(Vol. 6, p. 731), by Prof. Poulton of Oxford, andMimicry(Vol. 18, p. 495), by R. I. Pocock, superintendent of the Zoological Gardens in London, will suggest to the reader many objects for observation. Especially interesting in the former article is the section on the use of colour for warning and signaling. In connection with these articles, those onEgg(Vol. 9, p. 13) andFeather(Vol. 10, p. 224), by W. P. Pycraft, of the British Museum, may be read, andNidification(Vol. 19, p. 666), by Prof. Alfred Newton of Cambridge University, and Hans Gadow, Strickland curator and lecturer on zoology in the University of Cambridge; especially those sections concerned with the precautions taken by the birds for protection and concealment. A very fascinating subject is discussed in the articles dealing with the distribution and movements of animal life. These areZoological Distribution(Vol. 28, p. 1002), by the well-known zoologist Richard Lydekker;Migration(Vol. 18, p. 433), by Hans Gadow; andPlankton(Vol. 21, p. 720), by G. H. Fowler of University College, London. Reference to these articles has already been made in the chapter onBiology. Closely connected with them is the article onPalaeontology(Vol. 20, p. 579), by Prof. H. F. Osborn, Columbia University and American Museum of Natural History, in which the distribution of prehistoric life is discussed; and, as will be seen from the list below, all the principal species now only found in fossil remains are described in separate articles.
Intelligence of Animals
The editor succeeded in getting the psychologist, Prof. C. Lloyd Morgan, of the University of Bristol, who has made a specialty of this particular subject, to write extremely illuminating articles onInstinctand onIntelligence in Animals(Vol. 14, pp. 648 and 680). Interesting as throwing a side light on either the instinct or intelligence of birds, is the section on their song in the articleSong(Vol. 25, p. 413). It is hardly possible to look through any of these articles, or those on mimicry and colour, above alluded to, without coming across some striking and interesting fact, as for instance, the sudden change from a divine melody to an anxious croak in the utterance of the male nightingale as soon as the brood is hatched. These articles will be read for their great interest by many who do not intend systematically to pursue the subject of Zoology.
Animals in Captivity
The housing of animals in captivity is discussed in the articlesAquarium(Vol. 2, p. 237), by Professor G. H. Fowler, University College, London;Aviary(Vol. 3, p. 60), by D. Seth-Smith, curator of birds to the Zoological Society of London; andZoological Gardens(Vol. 28, p. 1018), by P. Chalmers Mitchell. The first two contain some very useful hints for the care of small aquaria and aviaries; and young people who like to have aquaria at home, and are often disappointed by their failure to keep alive some of their specimens, especially larval and other surface-swimming animals, will find one of their difficulties solved. These surface-swimming animals die of exhaustion from their unaided efforts to keep off the bottom, lacking the support given in their surroundings by the natural flow of the water, native tides, and surface currents. The article describes a very simple arrangement by which this motion of the water can be simulated.
Other articles which will be found very interesting are those onHibernation(Vol. 13, p. 441) and onIncubation and Incubators(Vol. 14, p. 359). In the latter many will be surprised to note that incubators have been in use in Egypt from time immemorial under the nameMamal. In one district of Egypt alone 90,000,000 eggs are annually hatched out in these old time incubators, of which the secret has been handed down, jealously guarded, from father to son. In the articleTaxidermy(Vol. 26, p. 464), Montagu Browne, a practical taxidermist, deals with the artistic as well as the technical aspects of the craft.
Classification and Divisions
Turning to the articles of the chief divisions of the animal kingdom, the most useful arrangement will be to enumerate them in their order. As has been already said, zoologists do not yet agree as to the best system of classification; the one which is given in the Britannica is that upon which the very eminent zoologists who have contributed the special articles, agree as being the most suitable. There are two main grades. TheProtozoa(Vol. 22, p. 479) contain the animalcules, mainly microscopic. These are the most elementary forms of life and consist of single cells. The other and more important grade is that of theMetazoa, which are built up of many cells.
Protozoa
The main subdivisions (called phyla) of the Protozoa are: phylum i.Sarcodina(Vol. 24, p. 208); phylum ii.Mastigophora(Vol. 17, p. 873); phylum iii.Sporozoa(Vol. 25, p. 734); phylum iv.Infusoria(Vol. 14, 557).
Metazoa
Coming next, the Metazoa in their order are, as follows: phylum i. Porifera (seeSponges, Vol. 25, p. 715); phylum ii.HydromedusaeorHydrozoa(Vol. 14, pp. 135 and 171) which include aquatic animals of the coral kind; phylum iii.Scyphomedusa(Vol. 24, p. 519) which include groups of shell fish; phylum iv.Anthozoa(Vol. 2, p. 97) with the corals; phylum v.Ctenophora(Vol. 7, p. 592) including the jelly fish; phylum vi.Platyelmia(Vol. 21, p. 826) a group of animals in which creeping first became habitual; phylum vii. Nematoidea (seeNematoda, Vol. 19, p. 359) which include certain kinds of worms; phylum viii.Chaetognatha(Vol. 5, p. 789) an isolated class of transparent pelagic organisms; phylum ix.Nemertina(Vol. 19, p. 363) worm families; phylum x.Mollusca(Vol. 2, p. 669) shell-bearing animals.
Phylum xi.Appendiculata(Vol. 2, p. 220) which include the sub-phylaRotifera(Vol. 23, p. 759),Chaetopoda(Vol. 5, p. 789), andArthropoda(Vol. 2, p. 673), the sub-phylum which comprises practically the whole insect family. Important articles on animals in this class are:Hexapoda(Vol. 13, p. 418) which include the wasp, beetle, and other families; theCrustacea(Vol. 7, p. 552) which cover a field wide enough to embrace species as different outwardly as lobsters, wood-lice, and minute water fleas; andArachnida(Vol. 2, p. 287) the spider family. Phylum xii.Echinoderma(Vol. 8, p. 871) with all the sea-urchins and star fish.
Phylum xiii.Vertebrata(Vol. 27, p. 1047) to which man belongs as an order of a sub-class of a class of a sub-phylum. The most important sub-phylum of the Vertebrata is the Craniata (see Vol. 27, p. 1048). The sub-phylaHemichorda(Vol. 13, p. 257), Urochorda (seeTunicata, Vol. 27, p. 379), and Cephalochorda (seeAmphioxus, Vol. 1, p. 886) deal with the lower orders of Vertebrata. The sub-phylum Craniata comprises the following classes: class i. Pisces, seeIchthyology(Vol. 14, p. 243) with the fishes; class ii.Batrachia(Vol. 3, p. 521), with the frog tribe; class iii. Reptilia (seeReptiles, Vol. 23,p. 136); and in close connection with this—class iv. Aves (seeBird, Vol. 3, p. 959, andOrnithology, Vol. 20, p. 299); class v.Mammalia(Vol. 17, p. 520) to which man belongs.
Phylum xiv.Mesozoa(Vol. 18, p. 187) minute parasitic animals intermediate between the Protozoa and the Metazoa. Phylum xv.Polyzoa(Vol. 22, p. 42) aquatic animals forming colonies by budding. Phylum xvi.Acanthocephala(Vol. 1, p. 109) including the parasitic worms. Phylum xvii.Podaxonia(Vol. 28, p. 1023), and phylum xviii.Gastrotricha(Vol. 11, p. 526) minute animals living at the bottom of ponds and marshes.
Natural History
This is an outline of the main division of the animal kingdom in their order as now classified. The subject of zoology is so vast that the student will probably confine himself to one branch of the subject, perhaps to one small fraction of a division, of which he proposes to investigate the complete natural history. As will be seen from the list below, which is classified, the Britannica offers an immense amount of material bearing on the subject. But of course the study of any one sub-class needs a general knowledge of the foundations of zoological science, so that some acquaintance with the principles on which the animal world is classified is indispensable. As in Botany, it will be easy to see from the article on any individual animal to which family it belongs so that the young student can work back from the particular to the general and find out the whole relationship of the subject in which he is interested by reference to the “systematic” article.