40 RENNERT: SEEDS AND SEEDLINGS OF ARISAEMA 
they are very abundant near the aleurone cells and become scarcer 
toward the embryo at the center of the endosperm. It will be 
seen that the only difference between the two seeds lies in the size 
of the cells which compose the aleurone layer and the seed coats. 
It follows from the greater size of the seed of A. Dracontium that 
this species has a food supply slightly greater than that of 4. “#7- 
phyllum. 
Both resting embryos occupy a position near the base of the 
seed. In fact the aleurone cells near the micropyle are obliterated 
and the base of the hypocotyl of each embryo is close to the teg- 
men at this point. The cavity in which the embryo lies, but does 
not entirely fill, corresponds in general shape to that of the embryo 
and extends as an axis from the micropyle to the hilar region 
through the center of the seed. Its sides are formed of starch- 
bearing cells, aleurone cells close to the cavity at the hilar end, 
while the tegmen bounds it at the opposite end as described above. 
The embryos are club-shaped and small in proportion to the 
amount of endosperm contained in the seeds. In A. Dracontium 
they are 2 mm. long and .75 mm. thick, while those of A. ¢iphyl- 
/um are slightly larger, measuring 2.75 mm. in length and .5 to 
.875 mm. in thickness. In A. triphyllum three fourths of the 
length of the embryo consists of cotyledon, the remainder is taken 
up by the hypocotyl. This relation is different in A. Dracontium, 
for the cotyledon in this case bears a slightly greater proportion to 
the entire length of the embryo. A slight constriction marks the 
insertion of the cotyledon on the hypocotyl, and a very small pro- 
tuberance at the base of the hypocotyl is the incipient radicle. 
Five regions are already differentiated in the resting embryo of 
each species, the dermatogen, procambium, root cap, meristem 
and fundamental parenchyma. The dermatogen is continuous 
with the epithelial layer which covers the entire embryo and, at 
the slit for the emergence of the plumule in the cotyledonary tube, 
is deflected back to line the plumular cavity. In the plumule of 
A, triphyllum dermatogen is already clearly differentiated but in 
A. Dracontium it is not so evident. The dermatogen is composed 
of a single row of narrow cells with their long axis at right angles : 
to the longitudinal axis of the embryo. They are filled with 
aleurone grains and each contains a crystalloid. The procambium 
Se 
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