Chapter V: Front Matter (5)

During the last forty or fifty years other botanists have attempted various systems of classification. In those of De Candolle, Endlicher, Lindley, and of Brongniart, the distribution of plants into groups is founded, as in those of Ray and Jussieu, on the consideration of the cotyledons; of the polypetalous, monopetalous, and apetalous flowers; finally, upon the mode of insertion of the stamens. Names have changed; things remain the same; and if in their details the series of families or orders present certain differences, it only arises from the fact that a linear series is incompatible with the natural system, and that the connection of the intermediate groups may be expressed in various ways without affecting the general principles of the system. “The formation of natural orders by Jussieu,” says Ad. Brongniart, “is even now a model which directs botanists in their studies to the affinity which connects the various forms of vegetation. Many of these orders have doubtless been subjected to important modifications, both in extending and limiting them; the numbers have been more than doubled; but the number of species now known is increased more than sixfold. Since the publication of the _Genera Plantarum_, many points in the organization of plants which were either scarcely touched upon or were altogether unsuspected, have now been considered, and it is found that they do not destroy, but confirm, and perfect the work of Jussieu. One is even astonished to find that the numerous discoveries in the anatomy and organography of plants since the beginning of the century have not introduced greater modifications into the constitution of the natural groups admitted by the author of the _Genera Plantarum_. It is here that we recognize the sagacity of the savant who established them, and the soundness of the principle which guided him.”

1, Edelweiss; 2, Nigella Arvensis; 3, Parnassia; 4, Rhododendron; 5, Ophrys Arachnites; 6, Cypripedium Calceolus; 7, Nepenthes; 8, Gnaphalium Dioicum; 9, Ophrys Muscifera]

The natural classification of plants, their distribution into families, well defined, and founded upon affinities, have been perfected and placed upon a basis more and more certain in our own days. Botanists have set themselves the task of unraveling and establishing the characters which dominate, and those which are subordinate, in each family; numbers have spread themselves over the globe, exploring the most distant regions, interrogating the solitudes of forests and plains which no European had hitherto visited, and have studied in their native wilds many exotic plants, comparing them with already known species, thus giving us a means of pointing out more precisely the tribes, genera, and species of each natural family. Monographs of a great number of such families have thus been written with great research. The study of the formation and evolution of organs; the discovery of the true mode of reproduction in cryptogams, still unknown in Jussieu’s time; the investigation of the inflorescence, of the fruits, of the ovules, of the embryos, have furnished elements for perfecting the limits of families and advancing natural classification.

Auguste Pyramus de Candolle is one of the botanists of the last century who has most contributed to the general adoption of natural families. His _Essai sur les Propriétés des Plantes_ is celebrated for the knowledge which it displays of the comparative physiological and medicinal action of vegetables, and the physical organization which naturally connects certain plants as a group. His _Prodromus Systematis Naturalis Regni Vegetabilis_, continued by his pupils and his son, is a wonderful work for the extent and precision of its details.

In Great Britain, from the days of Ray, we have always had zealous followers of the science of botany, more especially in the class which may be called field botanists. Withering, Sir James Edward Smith, and hundreds of followers more or less eminent, employed their leisure in the fascinating and healthy pursuit of plants, and perhaps the most valuable contributions to science are the detailed descriptions of species, with their habits and habitats, with which they have enriched our botanical literature. Nor was the study of the physiology of plants--a science which may be said to owe its existence to the researches of Grew and Malpighi--neglected. To the former belongs the merit of having pointed out the difference between seeds with one and seeds with two cotyledons, on which Ray founded the first division of his system of classification.

The German botanists have always been distinguished for their patient and laborious investigations; and it was reserved for the first of Germans, the poet Goethe, to effect the last great revolution that the ideas of botanists have undergone. In 1790, shortly after the appearance of De Jussieu’s _Genera_, he published a pamphlet on the _Metamorphoses of Plants_. At this time the functions of the organs of plants were supposed to be pretty well understood. The notion had, however, existed in a form more or less vague, from the times of Theophrastus, that the various parts of the flower were mere modifications of leaves, although their appearance was very different--a doctrine which Linnæus seems to have entertained at one time, as he speaks, in his _Prolepsis Plantarum_, of the parts of a flower being mere modifications of leaves whose period of development was anticipated. Goethe’s mind was, as he himself tells us, one more adapted to see agreements in things than to mark their distinctions. We are not surprised to find, therefore, that he takes up this theory, and demonstrates that the organs to which so many different names are applied--namely, the bracts, calyx, corolla, stamens, and pistil--are all modifications of the leaf: the bract being a contracted leaf; the calyx and corolla a collection or whorl of several; the stamens contracted and colored leaves; and the pistils leaves rolled up upon themselves and variously coherent.

These views of the poet met at first with little attention from botanists, and we are chiefly indebted to Robert Brown for the elucidation of Goethe’s theory. In his _Prodromus of the Plants of New Holland_, and in many papers in the _Linnæan Transactions_, he demonstrates its truth as well as its practical value; showing, by the use of the microscope, that the law was applicable not only to the external parts of plants, but that it was followed in their development also. Robert Brown contributed largely to perfecting the natural method of classification. His great work upon the flora of Australia has greatly extended the circle of our studies for that comparison of characters which is the basis of botanical genera and tribes.

The number of families of flowering plants admitted in the present day, as the result of the investigations of the eminent men whose names have been mentioned, and many others which could not be quoted here without swelling our pages to undue proportions, number three hundred and three; and many of these are again subdivided by botanists who have made certain families their special study.

The primary groups into which flowering plants are divided, and in which therefore the families or orders are themselves comprised in the classification at present accepted, being founded upon the degree of cohesion and adhesion in the petals and stamens, are undoubtedly somewhat artificial. The problem of how the orders are themselves to be combined into natural groups is one which still engages the attention of systematic botanists.

The vegetable kingdom is divided by Dr. Lindley into seven classes:

FLOWERLESS PLANTS (CRYPTOGAMS)

{ A Thallus is a fusion of root,
{ stem, and leaves into one general
{ mass, and Thallogens are
{ Stems and leaves { destitute of breathing pores,
I. THALLOGENS { imperceptible. { and multiply by the formation
{ of spores, in their interior or
{ upon their surface.

{ Beyond Thallogens are multitudes
{ of species, flowerless
{ like them, but approximating
{ to more complex structures,
{ sometimes acquiring the stature
{ of lofty trees with breathing
{ Stems and leaves { pores; their leaves and stems
II. ACROGENS { quite perceptible. { distinctly separated; they multiply
{ by reproductive spores
{ like the Thallogens. Their
{ stem, however, does not increase
{ in diameter, but at their
{ summit, as the name of the
{ class indicates.

FLOWERING PLANTS (PHANEROGAMS)

{ The Rhizogens are a collection
{ of anomalous plants,
{ mostly leafless and parasitical,
{ having the loose cellular organ-
{ ization of Fungi, although
{ traces of a spiral structure are
{ usually found among their
{ tissues. Some of them spring
{ directly from the shapeless cell-
III. RHIZOGENS { Fructification { ular mass which serves at once
{ springing from { for stem and root, and seems
{ a Thallus. { to be analogous to the Thallus
{ of the Fungi. Their flowers
{ resemble those of more perfect
{ plants; their sexual organs are
{ complete, but their embryo,
{ which is without any visible
{ radicle or cotyledon, simply
{ appears to be a spherical or
{ oblong homogeneous mass.

{ In Endogens the embryo
IV. ENDOGENS { Cotyledon single. { has but one cotyledon; the
{ Permanent woody { leaves have parallel veins; the
{ stem confused. { trunk contains bundles of spiral
{ Leaves parallel- { and dotted vessels, surrounded
{ veined. { by wood cells, arranged in a
{ confused manner.