542 STEVENS: DIOECISM IN THE TRAILING ARBUTUS 
maturity. In the formation of this cell a portion of one of the 
peripheral cells of the endosperm grows out into the tissues of 
the integument, increases greatly in size, and is later cut off by 
a cross wall. By the continual growth and division of the cell 
thus cut off, the micropylar haustorium develops rapidly until 
finally it consists of a group of eight or ten cells having dense 
granular contents and large nuclei. Frequently some of the cells 
of this haustorium contain two nuclei. The condition shown in 
FIG. 4 represents about the maximum development of the haus- 
toria, and in the nearly mature seed they appear crushed and 
distorted among the tissues of the integument. 
Haustoria of various kinds that function for the nourishment 
of the endosperm have been reported in numerous instances. Their 
occurrence and origin, together with the whole subject of the 
nourishment of the developing embryo sac, have been discussed 
by Coulter and Chamberlain (loc. cit. 104-113). They mention 
haustoria of various forms, developed from the micropylar and 
chalazal ends and even from the sides of the sac. Sometimes 
the haustoria develop from protrusions of the sac itself; but in 
other forms the synergids, the antipodal cells, the suspensor, and 
one of the row of megaspores have been reported to take part 
in the formation of haustoria. The structures found in Epigaea 
are noteworthy as rather simple haustoria which originate directly 
from the endosperm at a comparatively late stage in its develop- 
ment. 
BOTANICAL LABORATORY, 
YALE UNIVERsITY. 
LITERATURE CITED 
. Bastin, E. S. Structure of Epigaea repens. Am. Jour. Pharm. 
67: 231-236. 1895. 
- Coulter, J. M., & Chamberlain, C. J- Morphology of angio- 
sperms. New York, 1903. 
- Darwin, C. The different forms of flowers on plants of the same 
species. New York, edition of 1897. 
. Gray, A. Heteromorphism in Epigaea. Am. Jour. Sci. III. 12: 
74-76. 1876. (Same article) Am. Nat. 10: 490-492. 
. Guignard, L. La double fécondation chez les Solanées. Jour. de 
Bot. 16: 145-167. 1902. 
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