TRIPHYLLUM AND ARISAEMA DRACONTIUM 43 
cells of the endosperm. Here the diastase formed by the epithe- 
lium of the embryo can begin to act upon the stored starch of the 
seed and a proteolytic enzyme to dissolve the crystalloids. The 
starch of the endosperm is absorbed before the crystalloids, and 
when the cells in contact with the embryo have been emptied of 
their contents the cell walls are pushed back by the advancing 
growth of the cotyledon and the enzyme acts upon the contents 
of the cells next outside. The proteids of the aleurone cells do 
not become soluble until late in the history of the seedling. The 
cell walls of the endosperm do not seem to be acted upon by any 
enzyme, and are wholly intact until the seed separates from the 
seedling. 
While the epithelial cells are secreting the enzymes, the coty- 
ledon increases in length and by its elongation pushes the hypo- 
cotyl, bearing the stem-bud, through the seed coats at the mi- 
cropyle. A. Dracontium requires fully a month longer than A. 
‘riphyllum for its hypocotyl to protrude. When the hypocotyl 
has wholly emerged from the seed it is directed down into the 
ground at right angles to the plane of the cotyledon, which is still 
in the seed. This is effected by means of a bend in the cotyledon 
at the place where it leaves the seed. This downward pull of the 
hypocotyl serves to tilt the seed up, and is sufficient when the seed 
has not been planted deep to break through the ground and bring 
the seed to the surface. In all cases it loosens the earth about the 
seedling, and so renders it easier for the pumule to make its way 
through the soil. 
A great part of the cotyledon is confined within the seed during 
its entire development. The length which the cotyledons attain 
varies in both species, but those of A. Dracontium are on the aver- 
age shorter than those of A. sriphyllum. The average length of 
the 4. Dracontium cotyledons outside of the seed is 3 mm., while 
those of A. triphyllum reach an average length of 7 mm. The 
number of the cells in the cotyledon is not increased by its elonga- 
tion, for its entire growth is due to the increase in size of the 
already existing cells. The epithelial cells, which in the resting 
embryo had their axis perpendicular to the longitudinal axis of the 
embryo, now in the region of the cotyledon have this relation com- 
pletely changed. Their long axes are parallel with the longitudinal 
