CHAPTER VII.—ANGIOSPERMS. 
Since the classical researches of De Bary (’49) and Strasburger (’78, 
*79, ’84), especially the latter, the nature of the sexual process in the 
Angiosperms has been a matter of common knowledge among botanists, 
It is considered beyond the purpose of this work to discuss the subject 
historically, and no attempt will be made to present a summary of the 
various theories that have been advanced from time to time during the 
past half century upon the homologies of the female gametophyte or 
embryo-sac. The view held here is that pollen grains and embryo- 
sacs are respectively micro- and macrospores. The author is of the 
opinion, as will be seen from what follows, that the preponderance of 
morphological and cytological evidence indicates clearly that the pollen 
mother-cell and the embryo-sac mother-cell are undeniably homologous 
with the micro- and macrospore mother-cells of the archegoniates. 
The fact that the embryo-sac mother-cell is not provided with a special 
or well-differentiated cell-wall is almost without significance in deter- 
mining homologies. 
THE EMBRYO-SAC OR FEMALE GAMETOPHYTE. 
Although many variations occur among Angiosperms in the develop- 
ment of the embryo-sac, yet in the vast majority of cases this process 
may be reduced to two forms or types. Inthe one case a readily 
distinguishable hypodermal cell of the nucellus, either with or without 
giving rise to a tapetum, divides into an axial row of four (sometimes 
three ?) cells, or potential macrospores, the lowermost one developing 
usually into the embryo-sac. In the second case, which is typified by 
various species of Zz/ium, the hypodermal cell becomes at once the 
macrospore. As illustrating these two types respectively, the process 
of development will be described in Hedleborus fetidus, one of the 
Ranunculacex, and Lilium martagon. 
The macrospore mother-cell of Helleborus fatidus increases 
greatly in size, becoming much longer than broad in keeping pace 
with the growth in length of the nucellus. Its nucleus, which lies 
usually in the upper end of the cell, increases in size simultaneously, as a 
preparation for the first nuclear division. This period of growth ot both 
cell and nucleus corresponds to the period of growth immediately pre- 
ceding the first nuclear division in the pollen mother-cell (Fig. 70, A). 
The nucleus now divides, and, as a rule, there follows a division of 
