42 Rennert : Seeds and Seedlings of Arisaema 



starch. Scattered through the inner tissue are large cells filled 

 with proteids in which a crystalloid also is embedded. These pro- 

 teid cells are distributed through the tissues in those regions where 

 the pro-cambium strands first make their appearance. 



The embryos of the two species are similar in shape, position 

 in the seed and general structure. A. Dracontiinn differs from A. 

 fnpliyllmii in four particulars : (i) Its size, (2) The proportion 

 which the length of its cotyledon bears to its hypocotyl, (3) The 

 number of procambium regions to be found in the cotyledon and 

 (4) The state of differentiation of the procambium strands in the 

 plumule. Here already the tendency in A. Dracontiiun to delay 

 the development of the plumule is evident. 



The Germination of the Seedlings 



In both species when water reaches the seeds the mucilaginous 

 walls of the outer row of cells of the testa swell, while the cells 

 below, pulled out by the swelling outer row and pushed out by the 

 increase in size of the mucilaginous tegmen and the walls of the 

 aleurone cells, separate and show an irregular alternation of large 

 and small cells, which are, of course, empty. The seeds now in- 

 crease considerably in size by the absorption of water, and the action 

 of the moisture slowly reduces the outer row of the testa cells to 

 a gelatinous film about the seeds. The mucilaginous tegmen is 

 also soon dissolved, while all that remains of the seed coat is the 

 inner part of the testa. The tannin in the vesicles contained within 

 this becomes diffused through the whole of the cellulose coat and 

 makes it more resistant to the disintegrating action of the soil. 

 This part of the coat alone adheres to the seed until the last par- 

 ticle of endosperm is dissolved. The mucilaginous cells of the 

 seed coat and the thick walls of the aleurone cells serve to in- 

 crease the absorption of water, while the outer row of the testa is 

 instrumental in bringing about the attachment of the seed to the 

 soil.* The cellulose layer of the testa, impregnated with tannin, 

 protects the endosperm during germination. When water reaches 

 the embryo in the seed it swells and fills the cavity in which it lies, 

 so that its epithelial cells are in contact at the sides with the starch 



•* Klebs. Heilrage zur Morphologic und Biologie der Keimung. Untersuch. a. d. 

 Botan Institut z. Tubingen, i : 536. 1885. 



