267 
Dr. P. Bertrand on ZygopteridecB. 
explanation in the probability that so many of the fronds in 
question were sporophylls, destitute of any assimilatory expansions. 
The memoir is perhaps the best illustrated account of 
petrified plant-remains which has yet appeared. The atlas contains 
16 photographic plates; it is no exaggeration to say that every one 
of the 114 figures is a perfect reproduction of the section illustrated, 
while the preservation of the specimens is usually excellent. A 
certain number of very useful diagrammatic figures will further be 
found in the text. 
The value of Dr. Bertrand’s book depends greatly on the 
accurate observation of complicated detail, which could not be 
adequately discussed without the aid of a number of figures. All 
that can be done here is to give a sketch of his methods and con¬ 
clusions, with a few critical remarks. 
The starting-point of the exposition is the anatomy of the 
frond of Stauropteris oklhantia, to which Part I. (pp. 15-70) is 
devoted. The abundance of the specimens renders this species 
particularly favourable for working out the mode of branching of 
the rachis. Readers of The New Phytologist will be familiar 
with the main facts from Mr. Tansley’s second Lecture in his 
Course on the “ Evolution of the Filicinean Vascular System ” ; 
generally, a reference to that lecture will be the best preparation 
for the study of Dr. Bertrand’s book. 
The elaborate account of Stauropteris oldhamia (with which 
the more ancient species, S. burnt}slandica, P. Bert., is compared) 
is exceedingly interesting. The author has investigated in detail 
the peculiar mode of branching, tracing the exact course of the 
four protoxylem-groups, which, as he first showed, are not peri¬ 
pheral, but immersed in the corners of the wood. Like so many of 
the Zygopterideae, Stauropteris gives off two rows of branches on 
either side of its rachis, and this process is repeated, the successive 
planes of ramification being, in this case, parallel to one another. 
Every stage of branching is followed, up to the fine and simple 
ultimate branchlets which bear the sporangia. An interesting 
point is that concurrently with the main branching, small lateral 
strands are given off to supply the “ aphlebiae,” filamentous tufts, 
which have their homologue in many Zygopterideae and other fern¬ 
like plants of the Palaeozoic. 
The author’s account of the histology of the rachis on the 
whole confirms previous observations; he finds evidence of 
circinate vernation in the young frond. The sporangia are shortly 
