462 
EDWARD F. WOODCOCK 
become differentiated in the embryo, cell formation appears in the 
free endosperm, giving rise to the uniform layer of cellular endosperm. 
At the stage shown in figure 15, in which the cotyledons are becoming 
differentiated, this endosperm layer, EN, has become two cells thick, 
the outermost layer being differentiated into a "cambium" as in 
Polygonum Persicaria. The suspensor has become somewhat shriveled 
and the embryo imbedded in the layer of cellular endosperm lining 
the embryo sac. 
The growth of the endosperm from the stage just described pro- 
ceeds as in Polygonum Persicaria. At the stage shown in figure 16, 
the embryo is situated well down toward the base of the seed. The 
space about the embryo is continuous with a long narrow cavity, CF, 
extending to the micropyle. This cavity contains the shriveled 
remains of the suspensor and serves as a path for the later elongation 
of the hypocotyl. Figure i^j shows a later stage in which the hypo- 
cotyl and fleshy cotyledons have become quite well differentiated, 
and the cavity containing the shriveled suspensor has become some- 
what larger. 
The further growth and differentiation of the various tissues of the 
ovule proceed as in the type. The mature seed {figs. 18 and 19) 
which is 1.8 mm. long and .8 mm. wide, presents some differences 
in the tissues formed. At the micropylar portion of the aleurone 
layer {fig. i8a. A) appears an outer region consisting of prismatic 
cells containing dense granular contents, and an inner region con- 
sisting of irregular cells filled with a watery solution. The depleted 
condition of these cells has evidently been brought about through 
absorption by the surrounding tissues. The embryo, in its mature 
condition, is usually situated in an angle of the seed {fig. 19, C). 
The position of the embryo in this species seems to be quite as 
unstable a character as in Rumex, for, in a number of cases examined, 
the mature embryo occupied a position against one of the flat surfaces 
of the seed. 
The relatively long hypocotyl passes into the broader, fleshy 
cotyledons, which are elliptical in cross section and lie pressed 
against the base of the seed, with their faces at an angle of about 45 
degrees to a plane cutting the long axis of the seed at right angles 
{fig- 18, C). 
This position of the cotyledons is in marked contrast to the condi- 
tion found in Polygonum and Rumex. In P. Persicaria, P. Convolvulus, 
