1906] COOK—CUBAN NYMPHAEACEAE 383 
protoplasm is very dense and the cells at first divide rapidly, but 
no cell walls are formed (figs. 10, 33). After the embryo has passed 
the stage indicated in fig. 34, the endosperm appears to become 
thinner and does not stain readily until the embryo is near maturity. 
The protoplasm then becomes very dense, cell walls are formed, 
and one layer (occasionally two or three in Brasenia) of cells is 
developed which completely surrounds the embryo (jig. 40). This 
endosperm is usually thicker and forms two or more layers in a zone 
around the embryo at the point of origin of the cotyledonary lobes 
(jig. 38, x), and are very thin just below the root tip (fig. 38, y). It 
appears that the endosperm in Brasenia and Cabomba must perform 
a more important function in the germination of the embryo than 
in the species of the other genera. 
JOHNson (14) in his studies on Piperaceae has expressed the 
opinion that the “embryo sporophyte of the second generation is 
never nourished by the parent sporophyte directly, but always 
through the intermediate gametophyte.” The development and 
action of the endosperm in Nymphaeaceae confirms JOHNSON’S 
conclusions. : 
In all species studied there is a pronounced lateral enlargement of 
the embryo sac, at the expense of the nucellus, to accommodate the 
creasing endosperm and growing embryo (compare jigs. 24 and 25). 
EMBRYO. 
: The development of the embryo shows a very wide range of varia- 
tion. The embryo of Nymphaea advena (?) of Cuba follows almost 
exactly the same course as previously described by the writer for 
Nymphaea advena of the northern United States. The fertilized egg 
first divides transversely (fig. 12), and then two longitudinal walls 
result in a spherical embryo of eight cells. Successive cell divisions 
occur, but the spherical character is retained for some time, after 
Which there is an excessive growth on the side next to the micropyle, 
forming a suspensor by which the embryo is attached to the nucellus, 
and a flattening on the opposite side, thus giving the embryo the shape 
“ a short blunt cone, or rather of a pear (fig. 16). In this respect it 
differs from NV . advena of the north, in which the suspensor is much 
ore rudimentary and does not develop until much later. At this 
