458 
EDWARD F. WOODCOCK 
protoplasm, no intercellular spaces being present. Nearer the center 
the cells are larger, vacuolated, polyhedral and often binucleate, 
intercellular spaces also appearing. Numerous starch grains appear 
in the cells of this central tissue. Of the cells about the embryo only 
the distorted remains appear. Stevens (i8, p. 63, fig. 4) has repre- 
sented a similar condition for Fagopyrum esculentum. 
The differentiated outermost layer of the nucellus has persisted 
in an actively growing condition up to this stage keeping pace with 
the growth of the ovule. The cells of this layer have not divided, 
but the individual cells, except at the micropylar region, have become 
tangentially enlarged and vacuolated. As the embryo approaches 
maturity, these cells become more and more coarsely vacuolate, until 
in the mature seed only the crushed remains of this layer are evident. 
Stevens, p. 63, has figured a similar condition for Fagopyrum escu- 
lentum. The micropylar portion of this layer is made up of a single 
plate of much thicker cells undergoing no very appreciable change 
after the time of fertilization. Practically all of the remaining nucellar 
tissue has been destroyed, only a comparatively few crushed and 
distorted cells remaining around the haustorium-like structure earlier 
mentioned {fig. 3, iV). 
The persistence of the differentiated outer layer in an actively 
growing condition during the entire endosperm development, and the 
fact that it is characterized by dense granular contents, suggests that 
it serves a nutritive function. Coulter and Chamberlain (5, p. 178) 
have termed this layer the "nutritive jacket." The inner integument 
usually gives rise to this layer; however. Billings (2, p. 278), as one 
exception, describes, in Armeria plantaginea, such a layer, which he 
terms ''tapetum," as derived from the outer portion of the nucellus. 
Stevens (p. 62) has described in Fagopyrum esculentum a similar 
condition. Billings finds in Erodium gruinosum a "tapetum" made 
up of two layers, the inner one arising from the nucellus, and the outer 
from the integument. 
Lloyd (13, p. 103) has shown that in the date, nutritive material 
is distributed to the developing endosperm through the integuments 
to some extent. In P. Persicaria, however, the integuments ap- 
parently undergo very little differentiation, remaining as rather thin 
uniform structures, each consisting of but two layers of cells. As the 
ovule of P. Persicaria is furnished with no vessels for the transfer of 
nutritive material from the chalaza to the growing endosperm, it is 
