1909} BROWN—EMBRYO SAC OF HABENARIA 249 
that the fusion of the nuclei is connected with the fact that the nuclei 
have ceased developing and are in the same cell cavity. 
Summary 
The archesporium of Habenaria arises as a single hypodermal cell, 
which without dividing functions as a megaspore mother cell. 
The mother cell divides to two daughter cells and each of these to 
two megaspores. The division of the daughter cell nearest the micro- 
pyle is usually delayed. 
In some cases an embryo sac is probably formed from more than one 
megaspore; but the condition in the orchids, where there is a gradual 
reduction of the divisions of the megaspore mother cell without an 
indication of walls in the embryo sac, indicates that megaspore forma- 
tion may be omitted and the place of reduction changed to the first 
division of the nucleus of the embryo sac mother cell. 
The embryo sac of Habenaria contains eight nuclei: an egg, two 
synergids, two polar nuclei, and three ephemeral antipodals. 
The primary endosperm nucleus is formed by the fusion of the 
polar and second male nuclei, but degenerates without dividing. 
The absence of endosperm in many orchids offers no support to 
the view that the endosperm is a sexually produced embryo. 
The fertilized egg gives rise to a long suspensor and a globular 
embryo, 
: My thanks are due to Professor D. S. JoHNSON for helpful sugges- 
tons and criticisms. 
Jouns Hopxins UNIVERSITY 
Baltimore, Maryland 
LITERATURE CITED 
1. Brown, W. H., The nature of the embryo sac of Peperomia. Bor. GAZETTE 
LL, O. W., On ao tas of Lemna minor. Bot. GAZETTE 
27: 37-66. figs. 59. 1899. 
- Campsett, D. H., The embryo sac of Pandanus. 
36: 205-220. es 6 gee 1909. 
4. CoULTER AND CHAMBERLAIN, Morphology of angiosperms 80. 1903. 
) 
PEE 
Bull. Torr. Bot. Club 
w 
