83 Prof. A. Gray on Species considered as to 



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 the Oaks, by a very 

 careful, experienced, and conservative botanist, particularly con- 

 versant 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 orders might equally have 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 spe- 

 cimens in hand were distributed, according to their obvious re- 

 semblances, into groups of apparently identical or nearly iden- 

 tical forms, which were severally examined and compared. 

 Where specimens 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 conclusions from. Here, as DeCandolle remarks, 

 he had every advantage, being furnished with materials more 

 complete than any one person could have procured from hia 

 own herborizations, more varied than if he had observed a hun- 

 dred times over the same forms in the same district, and more 

 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 compara- 

 tive 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 intermediate 

 gradations ; characters stable in a limited number of instances, 



ganized beings, as respects origin, distribution, and succession. We are 

 not satisfied with the word, notwithstanding the precedent oi palceontology, 

 since ontology, the science of being, has an estabhshed meaning as referring 

 to mental existence, i. e. is a synonym or a department of metaphysics. 



