8i8 
Compton . — A/// Anatomical Study of 
Gain (’00). ’ The dicotyl is tetrarch (occasionally pentarch) ; tricotyls are 
either pentarch or hexarch. The behaviour of the individual vascular 
strands was not followed accurately ; the author remarks that the structure 
of the upper part of the hypocotyl of tricotyls ‘ rappelle tout a fait la 
structure de la region correspondante des plantules dicotylees ’ (p. 383). 
Hemitricotyls were also observed, and exhibited a pentarch symmetry 
(p. 388 ). 
General Remarks on Schizocotyly. 
In the case of syncotyly it was remarked that all degrees of the 
anomaly occur, from slightly attached cotyledons to complete fusion. The 
same is the case in schizocotyly, as has been emphasized by all writers on 
the subject. There can be scarcely any doubt that polycotyly and schizo- 
cotyly in the Angiosperms are one and the same phenomenon. The 
possession of three equidistant and equal cotyledons is the culmination 
of a series beginning with a slightly forked cotyledon ; there is probably 
not so much difference between complete tricotyly and advanced hemitrico- 
tyly in fact as there is in thought and speech. There is no warrant for 
assuming more than one process or tendency in schizocotylous races . 
though certain cases, perhaps owing to lack of adequate knowledge, may 
invite a meristic explanation (e. g. Lepidium sativum ). 
At one time I expected that the differences in genetic properties 
between different tricotylous races might be due to differences in the 
morphological nature of the anomaly ; but no real support for such a 
view has been obtained. It seems reasonable to think that schizocotyly is 
the mode of increase of the number of cotyledons in all the above cases. 
T. G. Hill and de Fraine (’08-T0), as a result of their extensive study 
of the seedlings of Gymnosperms, also see in schizocotyly the chief method 
by which the number of cotyledons has been increased from the primitive 
dicotylous condition. But two other methods are also supposed to have 
been employed. One of these is the shifting of a plumular leaf downwards 
into the cotyledonary whorl. The other method is of more interest in the 
present connexion ; certain seed-leaves were termed ‘ subsidiary cotyledons 
the criterion of this class of members being the fact that their vascular 
supply ‘ plays no important part in the formation of the root structure \ 1 
I have found some difficulty in understanding how far Hill and 
de Frame's subsidiary cotyledons constitute a morphological category: 
they say, for instance, that ‘ a subsidiary cotyledon may be promoted, as it 
were, to the rank of a half-cotyledon ’ 2 — a remark which appears to be 
unthinkable if taken in connexion with their further statement that ‘ the 
seed-leaves, as judged by the behaviour of their bundles in the transition 
region, naturally fall into three categories, viz. (a) whole cotyledons, 
1 Hill and de Fraine (’ 08 ), p. 708. 2 Loc. cit. (’ 09 ), p. 222. 
