THE NATURE OF THE EMBRYO SAC OF PEPEROMIA:® 
WILLIAM H. BROWN 
(WITH PLATES XXXI-XXXIII) 
At the suggestion of Professor Duncan S. JoHNson, I undertook 
the cytological study of the development of the embryo sac of several 
species of Peperomia, with the purpose of finding out whether the 
development of this genus offered any support to the idea, recently 
advanced by several investigators, that when a row of megaspores is 
not formed, each of the first four nuclei of the embryo sac is to be 
regarded as a megaspore nucleus. The results found were exceptional 
and may be of interest, as they seem to throw some light on this 
question and also on the nature of the embryo sac of Peperomia. 
For the investigation, Professor JOHNSON turned over to me mate- 
rial of three species which he had collected for this purpose. Mate- 
tial of P. arifolia was collected in the greenhouses in Baltimore. 
The material was fixed in chrom-acetic or Fleming’s solutions. The 
sections were cut 10 # thick and stained with Fleming’s triple or 
Haidenhain’s iron-alum hematoxylin. The latter stain was used 
alone or counterstained with gentian-violet or eosin. 
This paper does not pretend to be a study of the whole life-history 
of Peperomia, but deals in detail only with the development of the » 
embryo sac. It is hoped, however, that this will throw some light 
on the origin of the peculiarities which have been described in its 
later development. 
The sixteen-nucleate embryo sac of Peperomia was discovered in 
Peperomia pellucida by CAMPBELL (’99), who, however, misinterpreted 
some of its features. JOHNSON (’00) describes the mature sac of P. 
pellucida as containing one egg, one cell with the position of a syner- 
gid, six nuclei which are cut off singly against the wall of the sac and 
finally degenerate, and eight which fuse to form the endosperm 
nucleus. The archesporium consists of a single hypodermal cell which 
cuts off a single parietal cell and then forms the embryo sac. In a later 
t Contribution from the Botanical Laboratory of The Johns Hopkins University, 
O08, 
445] [Botanical Gazette, vol. 46 
