TRIPHYLLUM AND ArISAEMA DrACONTIUM 43 



cells of the endosperm. Here the diastase formed by the epithe- 

 lium of the embr)-o 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 nii- 

 cropyle. A. Dracontkini requires fully a month longer than A. 

 h-ipliylhnn 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 oi A. Dracontinin are on the aver- 

 age shorter than those of A. tripJiylluin. The average length of 

 the A. Dracoiitiinn cotyledons outside of the seed is 3 mm., while 

 those of A. tripltyl.iiin 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 



