26 6 
Review: 
layer ” and which now separates this from the protoplasm of the 
tapetum. We can, with the greatest certainty, observe that this 
new layer becomes the elater of the mature spore. The final layer 
of the spore-coat to develop is the endospore, which is produced 
within the exospore by the spore-protoplast. 
It will be seen, therefore, that the conclusion to be drawn from 
these observations is that the exospore and endospore are both 
products of the spore-protoplast, whilst the “ middle layer” and the 
elater are successively formed by the tapetal cytoplasm. 
In conclusion I may point out that the ripe spore contains a 
very considerable quantity of chlorophyll in its protoplast, and also 
that when these spores are heated with concentrated sulphuric acid 
on a cover-glass, very pretty siliceous skeletons are left behind. 
I have given above a brief outline of some features in the 
development of these spores, but a fuller account with illustrations 
will be published later. These observations were greatly facilitated 
by a Government Grant. Rudolf Beer, B.Sc., F.L.S. 
REVIEW. 
“ Etudes sur la Fronde des Zygopteridees ; par Paul Bertrand.” 
Lille, 1909. Text, pp. 286 8vo.; Atlas, Plates 16, pp. 35, 4to. 
HIS is in many respects a remarkable book. Probably no 
anatomical question relating to fossil plants, has ever been 
treated so fully before, nor has any one set of characters been so 
systematically and consistently utilized for theoretical purposes. 
The scope of the book is limited; it is concerned with the structure 
of the frond in a special family of Palaeozoic Ferns, and is 
practically confined to the anatomy and ramification of the 
vascular strands in the petiole and rachis, with only occasional 
references to other tissues. Little is said about the structure of 
the stem, nor is any account taken of stem-characters in the 
author’s classification and phylogenetic hypotheses. The frond is 
often the only part of the plant known, and so it is only upon this 
organ that a complete classification can be based ; to this extent 
the necessities of the case may justify a treatment of the subject 
which is inevitably one-sided. 
It is singular that throughout the book we have met with no 
reference to a lamina—a striking omission which may find a partial 
