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. Dracontiiim that 

 this species has a food supply slightly greater than that of A. tri- 

 pJiylliim. 



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. Dracontiuni 

 they are 2 mm. long and .75 mm. thick, while those oi A. tripliyl- 

 hun are slightly larger, measuring 2.75 mm. in length and .5 to 

 .875 mm. in thickness. In A. triphylhim 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. Draconthun, 

 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. tripliylluui dermatogen is already clearly differentiated but in 

 A. Dracontiuni 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 



