272 Dr. P. Bertrand on Zygopteridece. 
of the group among true Ferns ; the derivation of the later Fern- 
families from Zygopterideze is regarded as possible, but unproved 
(p. 255). 
The chapter on the Origin of the Zygopterideze is of great 
theoretical interest, for the author here develops an hypothesis (in 
general agreement with the views of Professor Potonie and Mr. 
Tansley) that the frond was primitively a branch of the axis, but 
has lost its original radial symmetry in becoming specialized for 
assimilatory functions. This idea is suggested, in the present 
connection, by the peculiar mode of branching of the Zygopteridean 
frond, which may be interpreted as a relic of primitive radial 
organisation. The theory is no doubt strengthened by the extensive 
observations of the author, showing how widespread are the 
peculiarities in question, but the reviewer is still inclined to suspect 
that these remarkable fronds were specialized rather than primitive 
organs. 
In Chapter IV. the important question of the relation of the 
Zygopterideze to the Cycadofilices is discussed, with special 
reference to the ancient type Calamopitys Saturni. The author 
comes to the conclusion that the two groups may be derived from a 
common source, i.e., from a class of Vascular Cryptogams in which 
the leaf or frond had not yet acquired its fundamental characters of 
symmetry and ramification (p. 279). It will be seen that this latter 
hypothesis again involves the assumption that the mode of branching 
of the Zygopteridean frond is a primitive character. 
It may be mentioned that the author fully recognises the 
analogy in the structure of the bundle between Lyginodendron or 
Calamopitys and the Cycads (p. 266), a point which has recently 
been disputed by Professor Chodat on the basis of the researches 
of the Bertrand school. 
Dr. Bertrand’s monograph is undoubtedly a most valuable 
contribution to the anatomical study of fossil plants. The some¬ 
what narrow scope of his work is fully compensated for by the 
accuracy and completeness with which it is carried out; though 
one may not always be convinced of the validity of the author’s 
interpretations, or of the security of his theoretical conclusions, his 
conscientious and acute investigations will have a permanent 
value, and will tend to raise further the standard of palzeobotanical 
research. D.H.S. 
R. Madley, Steam Printer, 151, Whitfield Street, London, W. 
