THE ENDOSPERM 257 



appearance of the nuclei in the cells of the endosperm. In the 

 earlier stages of development they appear to be in full activity and 

 their nucleoli are clearly visible, but with the gradual deposition of 

 starch in the cells the nucleoli disappear and the nuclei become 

 "deformed and squeezed out into networks of varying degrees of 

 coarseness" (Brenchley, 1912). Eventually they become com- 

 pletely disorganized or reduced to "amorphous lumps" and in the 

 mature seed even their remains can be made out only with the 

 greatest difficulty. In two recent studies dealing with the endo- 

 sperm of Agropyrum 11 and Triticum, Alexandra v and Alexandre va 

 (1938) have confirmed this degeneration of the nuclei and discussed 

 its implications in some detail. According to them, the disorgan- 

 ization of the nuclei occurs first and the deformation follows later, 

 owing to the pressure exerted on them by the surrounding starch 

 grains. They state that "cells with dying nuclei may continue to 

 live for some time," but the coordination between the activities of 

 the cytoplasm and plastids is disturbed. Further, "in fully ripe 

 grains the endosperm represents a physiologically dead tissue." Its 

 death is no disadvantage, however, for the embryo is supposed to 

 be able to secure the food materials necessary for its growth and 

 further development, more easily from a dead rather than a living 

 tissue, and the "dying off of the nuclei in the endosperm cells pro- 

 motes filling of the grain." 



Regarding the final fate of the endosperm, in some plants (Rici- 

 nus, Phoenix, Triticum, etc.) it forms a permanent storage tissue 

 which persists until the germination of the seed, while in others 

 (Cucurbita, Pisum, Arachis, etc.) it is used up by the growing 

 embryo and is no longer seen in the mature seed. 12 Of special 

 interest is Symplocarpus (Rosendahl, 1909) in which the embryo 

 "devours" not only the endosperm but also the two integuments, 

 so that it ultimately lies naked inside the wall of the ovary. An 

 even more extreme case is that of Melocanna bambusioides (Stapf, 

 1904), a member of the Bambuseae, in which the embryo dissolves 

 even the ovary wall so that it lies completely naked at maturity. 1 '" 



11 In this case the place of the degenerated endosperm nuclei is eventually taken 

 by druses of calcium oxalate, one in each cell. 



12 Many seeds, described in taxonomic literature as "exalbuminous," do have 

 small amounts of endosperm. Others, described as "albuminous," may have little 

 or no endosperm but a perisperm derived from the nucellus. 



13 In Cyanastrum (Fries, 1919; Nietsch, 1941) the nucellus and endosperm dis- 



