1 24 Brenchley. — On the Strength and Development of 
the embryo-sac, surrounding a central vacuole. Embedded in the lining 
plasm are, not two, but several nuclei, which are evidently the result of the 
division of the definitive nucleus, and hence are the early endosperm nuclei. 
These are quite free, no trace of cell walls appearing. Some series, notably 
those stained with Ehrlich’s haematoxylin and O. G., show the arrange- 
ment of nucellar and pericarp tissues very clearly. On the outer side of the 
regularly arranged boundary of the nucellus is a double layer, forming the 
inner integument of the ovule. Beyond this are two more rows of cells, 
thin-walled, and appearing rather crushed in places, which have sometimes 
remained in contact with the inner integument, sometimes with the inner 
layer of the pericarp in those preparations in which the ovule has shrunk 
away from the pericarp. This layer evidently represents the outer integu- 
ment of the seed, which gradually disappears in the course of development. 
The pericarp shows on its inner side one or two rows of regularly arranged 
cells with dense protoplasmic contents, beyond which occurs the larger- 
celled tissue containing much starch. The outer boundary is an epidermis 
of uniform cells, with much less starch, if any. 
By the next day, the third from pollination, evident progress has been 
made. The fertilized ovum has entered on a temporary resting-stage, and 
no change has yet occurred in it, while the synergidae have practically 
disappeared. The central vacuole has enlarged, and the nuclei embedded 
in the protoplasmic lining have greatly increased in number. These 
embryonic endosperm nuclei are multiplying at the expense of nutriment 
obtained from the nucellar tissue, the innermost cells of which have been 
emptied of their contents and are disorganizing, except at the tip of the 
grain, where they are being reserved for the future use of the embryo. 
The cells of the limiting layer of the nucellus have resumed their activity — 
many of the nuclei are in process of division, and some of the cells are 
narrow, only about half the normal width, showing that division has 
occurred, but the daughter-cells have not yet grown to their proper size. 
On the fifth day after pollination the first indication of division occurs 
in the fertilized egg cell. At this stage the future embryo lies at the tip of 
the grain in a little cid-de-sac formed by the nucellar tissue persisting in 
this region. In attendance on it is a dense mass of cytoplasm which is full 
of nuclei, while the protoplasmic lining of the embryo-sac contains very 
numerous nuclei characterized by the large number of nucleoli they possess ; 
as many as eight have been counted in some cases (cf. Cannon on Avena 
fatna , where the nuclei have from three to eight nucleoli). From this point 
onwards the development of the endosperm and embryo will be considered 
separately. The limiting layer or epidermis of the nucellus behaves some- 
what differently from the rest of the tissue. As previously stated, about 
three days after pollination the cells of which it is constituted renew their 
activity, nuclear division beginning again and continuing at a rapid rate, so 
