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 
ege, 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 lasting nourishing tissue is 
assumed by the enlarged hypocotyl. 
A similar development of endosperm 

Figure 27.— Portion of endosperm 
which lines embryo-sac, this par- 
ticular example being taken from 
the embryo-sac which contains 
the embryo shown in Pl. XIII, 
fig. 106. >< 575, 
appears in other Potamogetonaceae (Coulter and Chamberlain, 1903, 
pe 171): 
