OF CASTALIA ODORATA AND NYMPHAEA ADVENA 213 
protoplasm reaching back to the endosperm which never enters 
this tube (f 77, 78, 19 and ¢ext fig. r). The formation of this 
tube is in the axis‘of the ovule, where the nucellus cells are slightly 
elongated and have very thin walls. These cells are absorbed very 
readily, the fragments along the sides of the tube usually being 
very few and very small. The nucleus reaches the chalazal end 
of the ovule about the time the embryo is in?quadrant stage (eat 
Fic. 1, Tube formed by lower endosperm nucleus. Three-celled embryo and 
: in upper end of tube, lower endosperm nucleus in lower end of tube. Fig. 
19 drawn from same’section. 
Fg. 2). Upon reaching the chalazal end of the ovule the end of 
the tube enlarges, the cell making a corresponding enlargement 
_ and then degenerating (f. 20, a, 6). This process is complete 
- Sa the embryo and endosperm are in the stage represented by 
Bee her es 
