30 THE AMERICAN NATURALIST. [VoL. XXXIX. 
> 
other (Fig. 3). In the leptosporangiate ferns, the sporophore 
and root appear as adjacent outgrowths from the protocorm thus 
leaving the haustrum of the latter as a lateral cotyledon on one 
side of the metacormal axis (Fig. 4). 
Angiospermic embryos.— In the embryogeny of an angiosperm, 
a more or less massive protocorm is developed which may, or 
may not employ a suspensor. The form of the protocorm varies 
greatly, depending upon the shape and size of the seed, the extent 
and vigor of the endosperm, the duration of intraseminal devel- 
opment and the many other peculiar conditions presented by the 
seed habit. The sporophore arises as an outgrowth from the 
protocorm and its intraseminal development is, as a rule, quite 
restricted. The metacormal axis is always differentiated through 
protocormal tissue. (Figs. 5, 6, and 7.) 
In the monocotyledons, the sporophore primordium usually 
appears as a distinctly lateral outgrowth from the protocorm : 
but with the establishment of the metacormal axis between the 
sporophore and root the remaining protocormal tissue stands in 
a lateral position to this axis and, as a lateral cotyledon on one 
side of this axis, it functions during germination. As the spo- 
rophore primordium of a monocotyledon differentiates into the 
plumule the adjacent protocormal tissue grows forward around 
it, often completely enclosing it. 
In the dicotyledons, the protocorm early bifurcates and the 
sporophore primordium arises as an outgrowth between these 
two cotyledons which closely invest it during intraseminal growth 
(Fig.7). In many dicotyledons, a new structure, the hypocotyl, 
appears in the morphogenesis of the metacorm. The hypocotyl 
is differentiated between the root and sporophore from tissue 
which is phylogenetically haustral. During germination it serves 
to elevate the cotyledons and plumule. The cotyledons upon 
becoming exposed to the light usually become green and often 
function for a considerable time as photosynthetic areas. The 
assumption of the function of foliage leaves leads to the assump- 
tion of the form of such leaves, and the cotyledons of some 
plants approximate to a remarkable degree the form of: the later 
euphylls. 
Gymnospermic embryos. — That the gymnosperms in the ear- 
