319 
ferences, however grave, are supposed to have arisen from subse- 
quent variation, and the more marked differences to have become 
fixed through heredity. This ts included in the idea of spectes. 
Descent from a common stock explains the likeness, and is the only 
explanation of it,” p. 328, the italics are ours. “ Doubtless if varia- 
tion, such as botanists have to recognize within the species, be 
assumed as equally or even more operative through long antecedent 
periods, this would account for the diversification of an original spe- 
cies of a genus into several or many forms as different as those which 
we recognize as species. But this would not account for the limita- 
tion of species, which is the usual (but not universal) characteristic, _ 
and is an essential part of the idea of species,’ ibid.. We find here 
some obscurity ; the italics again are ours. Just this is accounted 
for by the Survival of the Fittest in the Struggle for Life. “Thus 
an ancestral type would become diversified into races and species. 
Earlier variation under terrestrial changes and vicissitudes, prolonged 
and various in geological times since the appearance of the main 
types of vegetation, and the attendant extinctions, are held to 
account for genera, tribes, orders, &c., and to explain their actual 
affinities. Affinity under this view is consanguinity ; and classifica- 
tion, so far as it is natural, expresses real relationship. Classes, 
Orders, Tribes, &c., are the earlier or main and successful branches — 
of the genealogical tree, genera are later branches, sfectes the latest 
definitely developed ramifications, varieties the developing buds.” p. 
329. ‘The italics ours. Add to this the note on page 319, where, dif~ 
fering from Darwin, Dr. Gray says: “‘ Naegeli, Brown and myself 
incline to the opinion that each plant has an inherent tendency to — 
variation in certain general directions,” and we havea tolerably com- 
plete presentation of his views on this subject. . 
The logician sometimes complains, when he finds, on analyzing a 
plant, that the description differs somewhat from the specimen before — 
him. We have so often met with these objections, that we are glad 
. to put the answer in Dr. Gray’s words, which are apposite for this — 
purpose, though having a more general intention. “The naturalist’s 
groups, of whatever grade, are not rea/sties, but ideas. Their consid-_ 
eration involves questions, not of /kéngs, between which absolute dis- _ 
tinction might be drawn, but of degrees of resemblance, which may be © 
expected to present infinite gradations.” : 
After discussing these questions, the chapter gives a particular 
account of the Linnaean classification, and a more general one of the 
Ante-Linnaean, and of the more noted Natural Systems. hy 
Chap. X., Phytography, gives rules for the description and naming 
of plants. Then follow directions for the collection, preservation, 
and examination of specimens. This may be called the Practical. 
Chapter of the book, and will prove one of the most interesting to the 
working botanist. We have never met with so complete information — 
on all points which a student who wishes to study, describe, or 
preserve his specimens, or to correspond with other botanists, wants 
to know about. To the section on Herborization Mr. Hoysradt 
contributes an abstract or new edition of his valuable notes, which 
