178 W. RALPH JONES 



This progressive solution of the starch was noticed by Sachs 4 

 in the cotyledons of the germinating bean. He believed that 

 the starch which was dissolved, and which diffused into a neigh- 

 boring cell, was there again deposited as starch. 5 While this doubt- 

 less occurs in other plant tissues, according to the work of 

 Rywosch on Vicia, and to my own studies on both Pisum and 

 Vicia, there is no evidence during germination for such repre- 

 cipitation. 



Gris 6 states that the solution of the aleurone in the endosperm 

 of Ricinus begins first at the periphery, and progresses inward 

 toward the inner face, i.e., that lying next to the cotyledons. 

 He, however, offers no explanation, merely remarking that' it is 

 "une exception singuliere" (p. 100). • Van Tieghem 7 also studied 

 the digestion of the aleurone of Ricinus seeds. He states that the 

 progressive solution "s'explique par la marche meme de l'eau 

 d'imbibition" (p. 187). 



Linz, in his work on the physiology of germination of maize 8 

 suggests that the similar phenomenon in the scutellum of maize is 

 caused by the lowering of the activity of the diastase in the internal 

 cells by the increase of osmotic pressure, due to the diffusion of the 

 sugar solution from the peripheral cells. Rywosch points out the 

 main objection to this theory, namely, that the osmotic pressure 

 is higher in the peripheral cells, where the diastase is obviously 

 most active, than in those lying nearer the center, for otherwise 

 the diffusion stream would not be centripetal. 



A consideration of the hypothesis of Van Tieghem suggests 

 several possibilities. Is there an enzyme already formed in the 

 ripe seed, or is it formed by the action of the water of imbibition 

 on the living protoplasm? In the former case, in the enzyme dis- 



4 Sachs, J., Physiologische Untersuchen iiber die Keimung der Schminkbohne. 

 Sitzungsber. Wien. Akad., Math. Nat. Hist. Klasse, 37: 57-119. 1859. 



5 Sachs, J. , Handbuch der Experimental-Physiologie der Pflanzen, p. 395. 1865. 

 6 Gris, A., Recherches anatomique et physiologique sur la germination. Ann. 



Sci. nat. Bot., V., 2: 5-123, p. 109. 1864. 



7 Van Tieghem, P. Sur la digestion de l'albumen. Ann. Sci. nat. Bot. VI, 4: 

 180-189. 1876. 



8 Linz, H., Beitrage zur Physiologie der Keimung des Mais. Jahrb. wiss. Bot. 

 29:267-319. 1896. 



