264 
TIIE JOURNAL OF I30TANY 
After a preliminary explanatory account of what is meant by the 
life-history of a Fern, a useful summary of the range of biological 
variations and morphological adaptations in the series, and a general 
review of the methods and ideas of classification—the last following 
the usual inverted order of older systematy,—the significant criteria 
of comparison are established as involving twelve points (p. 03). 
Each of these is then examined critically, to the extent of a chapter 
or more; the important conclusions are clearly stated, and the whole 
is bound together by a concluding section which summarizes the 
standpoint of the author, and the present position of the Class in the 
general story of Plant Evolution. 
Thus, an analysis of the shoot-system with its buds and branching 
gets as far as the conclusion that “ branching may be referred to 
dichotomy, with equal or unequal development of the resulting shanks, 
or to the formation of adventitious buds.” Dichotomy will hence be 
regarded as the primitive method for Ferns ; though any deeper reason 
for this is still left open. It is perhaps in the account of Leaf- 
Architecture that Professor Bower is at his best; and in dealing with 
the complexities of segmentation and venation helms laid the founda¬ 
tion for a comprehensive view of all leaf-construction in higher plants.’ 
The characteristic dichotomous venation of the great majority of 
Fern-types is convincingly shown, by series of ontogenetic comparison, 
to be the survival of what was once dichotomous ramification; now 
extended to a broadened lamina by phenomena of “webbing,” in 
which the original veins become secondarily connected, first by a 
marginal commissure, and subsequently by the addition of free ends 
and lateral branchings to a reticulate construction. It will be noted 
that this brings the primitive fern-frond into line with that of 
ArcluBocalamites ; the dichotomous venation of Ginkgo is evidently 
a stage in the same homoplastic progression ; while the familiar reti¬ 
culate venation of modern Angiosperms is probably but the end-term 
of a similar morphological series. Much of this beautiful work is for 
the first time introduced in text-book form. 
Chapters on vascular organization follow the academic lines of 
Stelar Theory. For teaching purposes, at any rate, it still seems 
impossible to escape from the mechanical schemes of Protostele and 
Medullation, Solenostely and Perforation, Dictyostely and Polycvcly. 
The leaf system of vascular strands is clearly traced from the 
cylindrical meristele to the horse-shoe section-pattern so characteristic 
of ferns, and phyletic primitiveness, or advance, may be judged 
according to the degree of disintegration. On the other hand, the 
root-characters are found to give little help in comparative study. 
Such stelar conceptions are admittedly based on evidence of so-called 
ontogenetic recapitulation ; and in Chapter X. a useful passage is 
introduced on the significance of size-relations between the conducting 
strands and the bulk of the tissues they supply. To this might have 
been added the difficulty in utilising the same S 3 r stem for organisms 
in which, though the volume of the adult may vary enormously from 
that of the younger plant, the general size of the tissue-units them¬ 
selves remains practically uniform; so that ontogeny is not necessarily 
