136 REVIEWS. 



spontaneous varieties and sub-varieties. The maximum is 

 found in Q. Rohiu\ with twenty-eight varieties, all spon- 

 taneous. Of Q. Lusltanica eleven varieties are enumerated, 

 of Q. CaUij)rinos ten, of Q. coccifera eight, etc. And he 

 significantly adds that " these very species which offer such 

 numerous modifications are themselves ordinarily surrounded 

 by other forms, provisionally called species, because of the 

 absence of known transitions or variations, but to which some 

 of these will probably have to be joined hereafter." The in- 

 ference is natural, if not inevitable, that the difference be- 

 tween such species and such varieties is only one of degree, 

 either as to amount of divergence, or of hereditary fixity, or as 

 to the frequency or rarity, at the present time, of interme- 

 diate forms. 



This brings us to the second section of De Candolle's article, 

 in which he passes on, from the observation of the present 

 forms and affinities of Cupuliferous plants, to the considera- 

 tion of their probable history and origin. Suffice it to say, 

 that he frankly accepts the inferences derived from the whole 

 course of observation, and even contemplates with satisfac- 

 tion a probable historical connection between congeneric spe- 

 cies. He accepts and, by various considerations drawn from 

 the geographical distribution of European Cupiiliferce^ for- 

 tifies the conclusion — long ago arrived at by Edward Forbes 

 — that the present species, and even some of their varieties, 

 date back to about the close of the Tertiary epoch, since 

 which time they have been subject to frequent and great 

 changes of habitation or limitation, but without appreciable 

 change of specific form or character ; that is, without pro- 

 founder changes than those within which a species at the 

 present time is known to vary. Moreover, he is careful to 

 state that he is far from concluding that the time of the 

 appearance of a species in Europe at all indicates the time 

 of its origin. Looking back still further into the Tertiary 

 epoch, of which the vegetable remains indicate many analo- 

 gous, but few, if any, identical forms, he concludes, with Heer 

 and others, that specific changes of form, as well as changes 

 of station, are to be presumed. And finally, that " the theory 



