THE EMBRYO SAC OF CASUARINA STRICTA. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 
ES 
THEODORE C. FRYE. 
(WITH PLATE XVII) 
In the examination of the embryo sac of Asclepias (2) the 
writer was impressed with the long resting period of the egg 
between its fertilization and its first division. The difficulty of 
distinguishing a fertilized from an unfertilized egg suggested that 
in some cases in which fertilization was reported to take place 
after the division of the endosperm nucleus, an error had crept 
in, an unfertilized egg being mistaken for a fertilized one. If 
there is fertilization after endosperm division, the fate of the 
second male nucleus is an equally interesting question. This 
suggested a reinvestigation of the sac of Casuarina, the results of 
which are here presented. 
The admirable paper of Treub (5) on Casuarina appeared in 
1891. Ina review of it by Chamberlain (1) in 1896, five years 
after it was published, the following suggestive statement is made: 
I have been deeply interested in Casuarina’s embryo sac without antipodals, 
as I have been studying Salix and for more than a year was unable to discover 
any trace of antipodals. However, Salix has antipodals, as some of my prep- 
arations now prove. Some slides also show the fushion of polar nuclei to 
form the endosperm nucleus. ‘There is no doubt that the antipodals of Salix 
are very transitory, but they are formed nevertheless. It may be that Casuarina 
has antipodals of this evanescent character. Since the technique betrayed by 
Treub’s figures and text could be greatly improved, I should be glad to see 
e Casuarina sac studied again in much greater detail, in order that Treub’s 
conclusion may receive additional confirmation or be corrected. 
A résumé of the more essential features of Treub’s paper is as 
follows: The species studied were C. suberosa, C. Rumphiana, and 
C. glauca. The pistillate flowers are naked, occurring in the 
eg of small bracts that form a cone-like cluster. Each pistil 
Consists of two carpels whose inner surfaces soon fuse along 
103! 101 
