62 BOTANICAL GAZETTE [JANUARY 
embryo sac (fig. 3). At the same time, the embryo is developing 
at the expense of the inner portion of the endosperm, so that the 
cells of the endosperm at this stage differ considerably in appearance. 
The ‘‘cambium”’ cells and the cells adjacent to them are thin-walled 
and closely packed. Nearer the center the cells become larger and 
vacuolate, some of them containing a considerable amount of starch; 
their walls also become slightly thicker, and the continued growth 
of the ovule pulls them apart, so that intercellular spaces of con- 
siderable size occur. Of the cells nearest the embryo only the 
crushed and distorted walls remain (fig. 4, £). 
Nearly all the nucellar tissue has been destroyed by this time. 
The differentiated outer layer, however, persists in an actively 
growing condition, differing from the earlier stages only in that the 
cells have elongated and show, in some instances, small vacuoles 
(fig.4,.N). This outer layer of the nucellus is apparently composed 
of two quite different regions, which grade insensibly into each 
other. The upper portion, around the micropyle, consists of a plate 
of cells which apparently undergo no change after the time of ferti- 
lization. The cells of the lower portion continue to grow actively 
with very little if any cell division. They increase somewhat in 
thickness, and to a very marked degree in surface extent, keeping 
pace with the growth of the young seed. As the embryo nears 
maturity, these cells become more and more coarsely vacuolate 
(fig. 5, V), and in the mature seed only the crushed remains of 
this layer are present (fig. 6, V). 
The fact that this layer persists in an actively growing condition 
till the growth of the endosperm is practically complete, together 
with the dense granular nature of the cell contents, suggests that 
it has a nutritive function, the “nutritive jacket” of CouLTER and 
CHAMBERLAIN (3, p. 103). Similar layers, presumably nutritive in 
function, have been observed in numerous instances. Usually 
this “nutritive jacket” is derived from the integument; in one case 
however, Armeria plantaginea, BILLINGS (1, p. 278) describes such 
a layer, which he calls a “tapetum,” as derived from the outer 
portion of the nucellus. In Erodium gruinosum Butuies finds 
this “‘tapetum” two layers thick, one layer of cells being derived 
from the integument and one from the nucellus. He describes 4 
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