No. 457.] EMBRYO OF THE ANGIOSPERMS. 21 
The ontogenetic origin of the cotyledons would seem to deny 
the foliar theory since they do not arise as exogenous lateral 
outgrowths upon the growing point of the stem as do all later 
foliar structures. Their appearance always precedes the differ- 
entiation of the stem-apex. 
Thus it appears that the foliar theory is supported only by 
the fact that in some plants the cotyledons are borne on a stem 
and are green, and may acquire a form resembling a leaf. It 
seems certain that any “unprejudiced " observer must at once 
admit that these are but superficial analogies ; quite insufficient 
evidence to warrant the conclusions so universally based upon 
them. 
To WHAT STRUCTURE, IF ANY, IN THE MONOCOTYLOUS 
EMBRYO ARE THE COTYLEDONS OF A Dicorvrous 
EMBRYO EQUIVALENT? 
Early embryologists considered the cotyledons of all angio- 
sperms (with the exceptions already noted) to be structures of 
the same category, morphologically as well as physiologically, 
and their conclusions have been accepted by botanists in general. 
Balfour (: o1), however, states that, * This terminal cotyledon 
in the Monocotyledons is not a leaf nor the homologue of the 
lateral cotyledons in the Dicotyledons." 
In this opinion he is again supported by Coulter and Cham- 
berlain (:03): * The current opinion regards it [the cotyledon] 
as a modified foliage leaf, and this is borne out in the majority 
of Dicotyledons by the assumption of the foliage function. The 
terminal cotyledon of Monocotyledons, however, seems to belong 
to a different category, and to hold no relation to a foliage leaf 
or to a foliar member of any description." To discover evidence 
which will in general prove the homology of the cotyledons, one 
has but to consult the recent works of Sterckx (’99), Lyon (:01), 
Cook (:02), Schmid (:02), Sargant (:02, :03, :04), Schaffner 
(:04) and York (:04). Just as the observations of the above 
mentioned investigators dispel all idea of such fundamental dif- 
ferences in the embryos as would indicate two types of different 
phylogenetic origin, so also do they show clearly that the coty- 
