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world is coextensive with Providence, and hold as firmly to the one as he does to the other, in spite of the wholly similar and apparently insuperable difficulties which the mind encounters whenever it endeavors to develop the idea into a system, either in the material and organic, or in the moral world. It is enough, in the way of obviating objections, to show that the philosophical difficulties of the one are the same, and onlv the same, as of the other.

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IV.

SPECIES AS TO VARIATION, GEOGRAPHICAL DISTRIBUTION, AND SUCCESSION,

(American Journal of Sciench and Arta, May, 1600.)

Etude sur l'Espèce, à l'Occasion d'une Révision de la Famille des Cupulifères, par M. Alphonse De CanDOLLE. This is the title of a paper by M. Alph. De Candolle, growing out of his study of the onks. It was published in the November number of the Bib liothèque Universelle, and separately issued as a pam phlet. A less inspiring task could hardly be assigned to a botanist than the systematic elaboration of the genus Quercus and its allies. The vast materials as sembled under De Candolle's hands, while disheartening for their bulk, offered small hope of novelty, The subject was both extremely trite and extremely difficult. Happily it occurred to De Candolle that an interest might be imparted to an onerous undertaking, and a work of necessity be turned to good account for science, by studying the oaks in view of the question of species.

What this term species means, or should mean, in natural history, what the limits of species, inter se or chronologically, or in geographical distribution, their modifications, actual or probable, their origin, and

their destiny-these are questions which surgo up from time to time; and now and then in the progress of science they come to assume a new and hopeful interest. Botany and zoology, geology, and what our author, feeling the want of a new term, proposes to namo epiontology,' all lead up to and converge into this class of questions, while recent theories shape and point the discussion. So we look with eager interest to see what light the study of oaks by a very careful, experienced, and conservativo botanist, particularly conversant with the geographical relations of plants, may throw upon the subject.

The course of investigation in this instance does not differ from that ordinarily pursued by working botanists; nor, indeed, are the theoretical conclusions other than those to which a similar study of other or ders might not have equally led. The oaks afford a very good occasion for the discussion of questions which press upon our attention, and perhaps they offer peculiarly good materials on account of the number of fossil species.

Preconceived notions about species being laid aside, the specimens in hand were distributed, accord

* A naine which, at the close of his article, De Candolle proposes for the study of the succession of organized beings, to comprehend, therefore, palmontology and all included under what is called geographical botany and zoology-the whole forming a selenco parallel to geology—the lat ter devoted to the history of unorganized bodies, the former, to that of organized beings, as respects origin, distribution, and succession. We are not satisfied with the word, notwithstanding the precedent of pala. ontology; luce ontology, the selence of being, has an established moan. Ing as referring to mental existence—I. o., Is a synonym or a department of metaphyslen.

ing to their obvious resemblances, into groups of apparently identical or nearly identical forms, which were soverally examined and compared. Where speci mens were few, as from countries little explored, the work was easy, but the conclusions, as will be seen, of small value. The fewer the materials, the smaller the likelihood of forms intermediate between any two, and-what does not appear being treated upon the old law-maxim as non-existent-species are readily enough defined. Where, however, specimens abound, as in the case of the oaks of Europe, of the Orient, and of the United States, of which the specimens amounted to hundreds, collected at different ages, in varied localities, by botanists of all sorts of views and predilections-here alone were data fit to draw useful conclu sions from. Here, as De Candolle remarks, he had every advantage, being furnished with materials moro complete than any one person could have procured from his own herborizations, more varied than if ho had observed a hundred times over the same forms in the same district, and moro impartial than if they had all been amassed by one person with his own ideas or predispositions. So that vast herbaria, into which contributions from every source have flowed for years, furnish the best possible data-at least are far better than any practicable amount of personal herborization -for the comparative study of related forms occurring over wide tracts of territory. But as the materials. increase, so do the difficulties. Forms, which appeared totally distinct, approach or blend through intermodiate gradations; characters, stablo in a limited number of instances or in a limited district, prove unstablo

occasionally, or when observed over a wider area; and the practical question is forced upon the investigator, What here is probably fixed and specific, and what is variant, pertaining to individual, variety, or race?

In the examination of these rich materials, certain characters were found to vary upon the same branch, or upon the same tree, sometimes according to age or development, sometimes irrespective of such relations or of any assignable reasons. Such characters, of course, are not specifle, although many of them aro such as would have been expected to be constant in the same species, and are such as generally enter into specific definitions. Variations of this sort, De Candolle, with his usual painstaking, classifies and tabulates, and even expresses numerically their frequency in certain species. The results are brought well to view in a systematic enumeration:

1. Of characters which frequently vary upon the same branch: over a dozen such are mentioned.

2. Of those which sometimes vary upon the same branch: a smaller number of these are mentioned.

3. Those so rare that they might be called nonstrosities.

Then ho enumerates characters, ten in number, which he has never found to vary on the same branch, and which, therefore, may better claim to be employed ns specific. But, as among them ho includes the dura tion of the leaves, the size of the cupule, and the form and size of its scales, which are by no means quite uniform in different trees of the same species, even theso characters must be taken with allowance. In fact, having first brought together, as groups of the lowest

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