44 Rennert : Seeds and Seedlings of Arisaema 



axis of the embryo. The cells of the parenchyma have also taken 

 on an elongated form. The only region in the cotyledon where 

 new cells are added is that occupied by the procambium and fibro- 

 vascular bundles. Here the cell division is very active. Radial 

 growth takes place only as the contents of the endosperm cells is 

 absorbed. The shape, arrangement of cells and manner of elon- 

 gating are exactly similar in the cotyledons of A. Dracontmm and 

 A. triphylhnn. It is only in the fibrovascular system that any dif- 

 ference between them has been discovered. Here in both cases, 

 as in the procambium strands in the embryo, the bundles near the 

 tip, branch and anastomose so that their distribution is irregular. 

 At the base, however, the number of bundles is constant. A. Dra- 

 contium as a rule possesses six bundles : one of these strands is very 

 weak and occupies the same position as the sixth procambium strand 

 in the cotyledon, /. e., at the right of the largest central bundle. The 

 left hand strand which corresponds to the seventh in the resting 

 embryo disappears before the cotyledon has proceeded very far 

 with its development. The cotyledon of A. tripliyllujii has five 

 bundles arranged as in the resting embryo. In a few instances 

 chlorophyl has been found in that part of the cotyledon of A. 

 Dracont'mni which protrudes from the seed both when the plumule 

 was functional and when it was not. These cases, however, are 

 uncommon. 



Up to this point there is almost absolute identity in the germi- 

 nation of these two species : the only difference between them lies 

 in the various sizes which the cotyledons attain. After this stage 

 in the germination has been reached, however, various differences 

 in the order of development of the organs become apparent. 



The rudiments of all the structures of the mature corm are 

 present in the hypocotyl of both A. triphylhan and A. Dracontiiwi 

 and the formation of the corm is brought about by the enlarge- 

 ment of the base of the hypocotyl and the laying down in it of the 

 definitive tissues. In both it increases in bulk at least to a small 

 extent before the first primary root is sent out. The hypocotol 

 of A. Dracontmm enlarges at a very much more rapid rate in the 

 first stages of germination than does A. triphyLlum and generally 

 attains a considerable development before the root appears. A 

 seedling o{ A. Dracoiitiiim with two roots each only i mm. in length 



