546 
Note. 
A further difficulty lay in the germination of the seeds themselves, many of which 
are tropical. Even when the optimum conditions of heat and moisture were provided, 
many foreign seeds, for other reasons, did not germinate. It may be that they had 
been stored for too long a time and had lost the power of germination, or perhaps 
other and biological conditions necessary to germination were not supplied. 
Again, it is not possible in all cases to determine with certainty that what might 
be regarded as a stoma initial will prove to be so, without following out its development 
during the further growth of the cotyledon. In several observed cases the supposed 
stoma initials have not developed into stomata on germination. Presumably this may 
be either because they were really ordinary epidermal cells with a superficial resem- 
blance to stoma initials or because they have lost the power to undergo further 
division. This explanation may possibly apply to the case of the genus Lathyrus . 
According to Lubbock, Goebel, Hildebrandt, Janczewski, and others, there are : 
(1) Several orders in which all species show epigeal cotyledons, e. g. Cruciferae, 
Scrophulariaceae, &c. 
(2) A few orders in which all species possess hypogeal cotyledons, e. g. Nym- 
phaeaceae, Guttiferae, &c. And, on the other hand, there are : 
(3) Genera with species, some of which have hypogeal and others epigeal 
cotyledons. This third class is particularly interesting, seeing that one might reason- 
ably expect to find stoma initials present on all such cotyledons before germination. 
According to the authorities cited, the following are to be included under this head : 
Clematis , Anona , Rhus, Trichosanthes , Ardisia, Jatropha , Rhamnus , Mercurialis, 
Phaseolus, Erythrina , Anemone , Ahrus. Species of those genera that have so far been 
examined give evidence in support of this view. 
More than forty types of seeds have already been investigated. It is hoped later 
to give a complete account of these examples and of such others as it may be possible 
to obtain, both as regards the occurrence of stoma initials or fully developed stomata 
before and after germination, and also to correlate this anatomical feature with 
the morphology of the cotyledons. 
The hypogeal cotyledons of the seeds examined fall into three categories : 
(1) Those in which definite stomata are formed within the testa before germina- 
tion, e. g. Pachyrhizus angulaius, Phaseolus multiflorus. 
(2) Those in which stoma initials are present, which develop into stomata 
on germination, e. g. Citrus decumana. 
(3) Those in which no stoma initials are present or, if present, have lost the 
power of further development, e. g. Pisum sativum , Tropaeolum minus. 
In many such species the first two or three pairs of true leaves are reduced 
to mere scales, e. g. Walsura piscidia , Calodendron capense. 
The seeds used in this investigation have been provided by the Directors of the 
Royal Botanic Gardens of Kew, Edinburgh, Calcutta, and Trinidad. 
ELSIE M. BLACKWELL. 
Hartley Botanical Laboratories. 
University of Liverpool, 
March , 1914 . 
