L82 BARWINIANA. 



order, those forms which varied upon the same stock, 

 he next had to combine similarly various forms which, 

 though not found associated upon the same branch, 

 were thoroughly blended by intermediate degrees : 



"The lower groups (varieties or races) being thus consti- 

 tuted, I have given the rank of species to the groups next above 

 these, which differ in other respects, i. e., either in characters 

 which were not found united upon certain individuals, or in 

 those which do not show transitions from one individual to an- 

 other. Tor the oaks of regions sufficiently known, the species 

 thus formed rest upon satisfactory bases, of w T hich the proof can 

 be furnished. It is quite otherwise with those which are repre- 

 sented in our herbaria by single or few specimens. These are 

 provisional species — species which may hereafter fall to the rank 

 of simple varieties. I have not been inclined to prejudge such 

 questions ; indeed, in this regard, I am not disposed to follow 

 those authors w r hose tendency is, as they say, to reunite species. 

 I never reunite them without proof in each particular case ; 

 while the botanists to w r hom I refer do so on the ground of 

 analogous variations or transitions occurring in the same genus 

 or in the same family. For example resting on the fact that 

 Quercus Ilex, Q. coccifera, Q. acutifolia, etc., have the leaves 

 sometimes entire and sometimes toothed upon the same branch, 

 or present transitions from one tree to another, I might readily 

 have united my Q. Tlapuxahuensis to Q. Sartor ii of Liebmann, 

 since these two differ only in their entire or their toothed leaves. 

 From the fact that the length of the peduncle varies in Q. Bo- 

 bur and many other oaks, I might have combined Q. Seemannii 

 Liebm. w r ith Q. salicifolia Nee. I have not admitted these in- 

 ductions, but have demanded visible proof in each particular 

 case. Many species are thus left as provisional ; but, in proceed- 

 ing thus, the progress of the science will be more regular, and 

 the synonymy less dependent upon the caprice or the theoretical 

 opinions of each author." 



This is safe and to a certain degree judicious, no 

 doubt, as respects published species. Once admitted, 



