24 Campbell. — The Development of the Flower and 
The Endosperm. 
The formation of the endosperm begins shortly after fertili- 
zation. The primary endosperm-nucleus divides in the upper 
part of the embryo-sac, and the derivative nuclei distribute 
themselves in the layer of protoplasm lining its wall. The 
number of nuclei is large, and the protoplasmic layer becomes 
a good deal thickened, but no cell-divisions were seen in the 
endosperm. The nuclei are distinct, each with a single con- 
spicuous nucleolus (Fig. 44, a), and vary a good deal in size. 
The embryo finally fills the embryo-sac completely, and in 
the mature seed there is no trace of the endosperm. 
Summary. 
1. The flowers of Lilaea are of strictly terminal origin, 
both anther and ovule being formed directly from the trans- 
formed apex of the shoot. 
2. The sporogenous tissue of the stamen is not hypodermal 
in its origin, but arises from the plerome, as in Naias and 
Zannichellia. 
3. The ripe pollen-spore has two cells. The generative 
nucleus remains undivided in the ripe spore. 
4. The archesporium of the ovule is hypodermal, and a 
tapetal cell is cut off from it. 
5. The primary sporogenous cell of the ovule divides 
usually into three, of which the middle one becomes the 
embryo-sac. 
6. The embryo-sac usually develops in the manner typical 
of the Angiosperms, but there may be a suppression of 
a definite egg-apparatus, and a formation of cellular tissue in 
the upper part of the embryo-sac before fertilization. This 
is probably accompanied by an increase in the number of 
nuclei, such as has been observed in other low Mono- 
cotyledons. 
7. The first division of the embryo is the typical one into 
