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Updated: May 10, 2025
The sameness of fresh-water productions all over the globe is not confined to animal life, but extends to plants also. Alphonse de Candolle has remarked that in large groups of plants which have many terrestrial and only a few aquatic species the latter have a far wider distribution than the former. D. Sharp informs me that water-beetles undoubtedly present the same types all over the world.
Of the twenty-eight spontaneous varieties of Q. Robur, which De Candolle recognizes, all but six, he remarks, fall naturally under the three sub-species, pedunculata, sessiliflora, and pubescens, and are therefore forms grouped around these as centres; and, moreover, the few connecting forms are by no means the most common.
Doubtless a species may rightfully be condemned on good circumstantial evidence. But what course does De Candolle pursue in the case of every-day occurrence to most working botanists, having to elaborate collections from countries not so well explored as Europe when the forms in question, or one of the two, are as yet unnamed?
Concluding we may state that according to the whole evidence as it has been discussed by De Candolle and especially by Cook, the coconut-palm is of American origin and has been distributed as a cultivated tree by man through the whole of its wide range. This must have happened in a prehistoric era, thus affording time enough for the subsequent development of the fifty and more known varieties.
The species of all kinds which inhabit oceanic islands are few in number compared with those on equal continental areas: Alph. de Candolle admits this for plants, and Wollaston for insects.
Besides the direct comparison of the mutations described in our former lectures, with the analogous cases of the horticultural and natural production of species and varieties at large, another way is open to obtain the required proof. It is the study of the phenomena, designated by Casimir de Candolle by the name of taxonomic anomalies.
Quercus Ilex, the evergreen oak of Southern Europe and Northern Africa, reveals a similar archaeology; but its presence in Algeria leads De Candolle to regard it as a much more ancient denizen of Europe than Q. Robur; and a Tertiary oak, Q. ilicoides, from a very old Miocene bed in Switzerland, is thought to be one of its ancestral forms.
Being familiar with the fact that many species, naturalised through man's agency, have spread with astonishing rapidity over new countries, we are apt to infer that most species would thus spread; but we should remember that the forms which become naturalised in new countries are not generally closely allied to the aboriginal inhabitants, but are very distinct species, belonging in a large proportion of cases, as shown by Alph. de Candolle, to distinct genera.
Rossi and Sismondi were busy lecturing to the Genevese youth, or taking part in Genevese legislation; an active scientific group, headed by the Pictets, De la Rive, and the botanist Auguste-Pyrame de Candolle, kept the country abreast of European thought and speculation, while the mixed nationality of the place the blending in it of French keenness with Protestant enthusiasms and Protestant solidity was beginning to find inimitable and characteristic expression in the stories of Toepffer.
The cockscomb or Celosia is one of the most notorious instances. Cauliflowers, turnips and varieties of cabbages are recorded by De Candolle to have arisen in culture, more than a century ago, as isolated monstrous individuals. They come true from seed, but show deviations from time to time which seem to be intimately linked with their abnormal characters.
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