The Morphology of Ruppia Maritima. 



145 



Endosperm 



The endosperm nucleus is large, and located near the antipodal 

 end of the embryo-sac, or sometimes near the center. Just what 

 nuclei enter into its formation was 

 not ascertained, nor could I deter- 

 mine whether or not in the matter 

 of commencing division it has a 

 slight advantage over the fertilized 

 egg, as Murbeck (1902) declares is 

 the case in Ruppia rostellata. 



The endosperm in its most fully 

 developed stage (Text-fig. 27), is 

 never more than a thin layer lining 

 the embryo-sac and containing free 

 nuclei. In the mature seed, traces 

 of it may still be seen as a thin 

 protoplasmic lining, with the nuclei 

 now much reduced in size. Thus 

 it is clear that the endosperm is 

 here only temporary. The function 

 of more lastiiag nourishing tissue is 

 assumed by the enlarged hypocotyl. 

 A similar development of endosperm 

 appears in other Potamogetonaceae (Coulter and Chamberlain, 1903, 

 p. 171). 



Figui'e 27. — Portion of eudosperni 

 w^hich lines embryo-sac, this par- 

 ticular example being taken from 

 tke embryo-sac -which contains 

 the embryo shown in PL XIII, 

 fig. 106. X 575. 



