22 ARISAEMA TRIPHYLLUM 
is withdrawn from the lateral portions and much from the basal 
portion of the nucellus. From the maturity of the embryo-sac 
to the time of fertilization starch is rapidly stored in the integu- 
ments, except in their upper portions. Both the integuments 
become considerably thickened, and the inner one shows a peculiar 
elongation of the cells bordering the basal portion of the embryo- 
sac and nucellus (PLATE 2, FIG. 28). A like increase in size of the 
cells of the basal nucellar tissue is also noticeable at this time 
(PLATE 2, FIG. 27). These cells, as well as those of the integuments, 
become well filled with starch, especially if fertilization does not 
take place until late. The changes so far noted are not in any 
way the result of stimuli connected with pollination or fertiliza- 
tion, as is shown by the fact that they occur to a noticeable extent 
in ovules of flowers protected from possible pollination, and in 
ovules which have failed to develop any embryo-sac, as is the case 
shown in PLATE 2, FIG. 27. 
After fertilization has taken place the thickening of the integu- 
ments and the accompanying gathering of the starch continue for 
some time. As is described in connection with the history of the 
endosperm, very shortly after the organization of the vegetative 
nucleus in the residual cavity, the basal nucellar mass is destroyed. 
The subsequent increase in the size of the whole embryo-sac cavity 
is due to pressure of rapidly increasing cell sap. At the same time 
the food from the integuments is transferred to the residual cavity 
and thence to the endosperm and embryo. As a result of this 
expansion and food transfer the inner integument is reduced to a 
sheath of dead empty cells, crushed against the outer integument. 
The food is withdrawn from the second integument by way of 
the chalaza, and the inner cells crushed. Before this is ac- 
complished the four outer layers of cells form thick cutinized 
walls (TEXT FIG. 27), and so produce 
a firm outer covering of the seed. 
Many of the cells of the outer integ- 
. 27. Epidermis and un- ument become filled with a tannin 
matic cells with thick walls compound, which Rennert (22) has 
ie apni meee TE noted as a preservative measure at 
the time of germination. The cell 
walls of the integuments persist so that the mature seed is sur- 
Siti ea E 
Be a ee Sele as 
