NOTES. 
THE COTYLEDONS OF GINKGO BILOBA AND CYCAS 
REVOLUTA. Mr. Lyon, in discussing the phylogeny of the coty- 
ledon in the journal Postelsia (1901), has come to the conclusion that the 
so-called cotyledons of the Pteridophyta and Gymnosperms, with” the 
probable exceptions of Ginkgo and the Cycads, are true foliage leaves. 
The foliar nature of the ‘ cotyledons ’ of Ginkgo and the Cycads 
would seem from this still open to discussion. The alternative would 
be the interpretation of these cotyledons as feeders, the term applied 
by Prof. Bower to the absorptive organs of the Gnetaceae. 
Apart from the obvious double structure of the absorptive organs in 
Ginkgo and Cycas, which clearly distinguishes them from the feeders 
of the Gnetaceae, and would suggest their foliar nature, there are other 
features which may, I think, be taken to indicate that they are much 
modified foliar organs. Among these characters one I have recently 
observed is the occurrence of stomata on these cotyledons. 
In Ginkgo the cotyledons are surrounded by endosperm but not 
fused with it. Their inner surfaces are closely pressed together so that 
each appears semi-circular in transverse section ; sometimes only the 
margins meet, and then the cotyledons appear almost crescentic in 
transverse section. 
Stomata are found chiefly on the upper surface, while in the foliage 
leaves they occur on the lower side only. This may be explained 
either by supposing those on the under surface of the cotyledons to 
have disappeared owing to the absorptive function of that part of the 
cotyledons, or, if we assume that the cotyledons were at a former period 
in the history of the plant expanded above ground, the stomata on the 
upper surface may have been protected by closing movements of the 
cotyledons similar to those of Cucurhita. 
[Annals of Botany, Vol. XVII. No. LXV III. September, 1903.] 
