93 
and Affinities of Trapella. 
As the endosperm is developing, we find that its upper 
layers have their cells arranged in strata, more or less parallel 
to the base of the synergidal region (/. d. Fig. 36). The cells 
making up the layers in question are large and conspicuously 
granular, with large, well-defined nuclei ; and in later stages 
their walls become thickened and lignified. In this way a 
diaphragm is formed across the embryo-sac, absolutely cutting 
off the synergidal region from that which is occupied by the 
endosperm and embryo. 
In Fig. 36 are seen the preparations for this diaphragm, 
i. e. the parallel rows of cells, /. d. : in Figs. 37 and 38 the walls 
of these cells constituting the diaphragm have become ligni- 
fied and are drawn in black (/. d.). The transition from the 
lignified diaphragm to the non-lignified normal endosperm 
below it is as sudden as it is represented as being in the 
figures. At the most, the diaphragm is five or six layers 
deep. 
We find in the adult seed that its narrowest part cor- 
responds to this diaphragm (Fig. 35 and 37). This is due to 
the fact that the other parts go on expanding (corresponding 
to the growth of the embryo &c.) after the diaphragm has 
become hardened and non-extensible ; hence in this region 
a circular constriction is formed. The development of such 
a barrier is, doubtless, to prevent any contamination of the 
embryo and endosperm in which it lies, by the death and 
possible subsequent decay of the synergidae. 
It may be that these enlarged synergidae in some way 
assist in the absorption of food-material from the placenta 
just as the appendage at the other end does from the tissues 
of the nucellus and integument. Indeed the occurrence of 
such a sucker at one end of the embryo-sac does not render 
it at all less probable that there will be one at the other. 
It is interesting to compare the respective morphological 
values of the two special organs in question, in the one 
case a cap-cell, in the other the synergidae, and to notice how 
by a special adaptation they play, on this view, identical 
rotes. 
