1899] STRUCTURE OF THE EMBRYO-SAC 161 
have increased in volume. As in Sparganium, the latter are 
much more granular than the egg-cell, but there is less differ- 
ence in size than is the case in Sparganium. 
In the specimen which is shown in Jig. 14, which was prob- 
ably ready for fertilization, the two polar nuclei were still sepa- 
rate, but whether they fuse before fertilization is effected must 
remain for the present undecided. 
The subsequent history of the embryo-sac in Lysichiton dif- 
fers strikingly from that of Sparganium.- There is a formation 
of free nuclei resulting from the division of the primary endo 
sperm-nucleus, but this is early followed by the formation of 
division-walls which extend entirely across the lumen of the 
embryo-sac, and this soon becomes completely filled with the 
large-celled endospermal tissue (figs. 75,76). This filling of 
sy embryo-sac with a continuous tissue seems to be characteris- 
lc of most of the aroids hitherto examined, and recalls the 
Structure of the prothallial tissue in Selaginella or Isoétes. The 
ar Pe of endosperm has also been observed in various 
dicotyledons, : 
of ‘e <Orarpage as in Sparganium, there is a marked growth 
rapidly se ae subsequent to fertilization. They enlarge 
ieee vide, but the number is never large (the specimen 
finely ore eight). The cytoplasm of the antipodal cells is 
sis Pape and they are doubtless of physiological impor- 
ais a “alae as in the case figured (fig. 17), the antipo- 
are a. early separated from the basal endosperm cells which 
The apa but this is not always the case. 
the cons . €1 of the older antipodal cells become very large, and 
less ae te de the younger nucleus becomes much 
€ appearan € actual division of these nuclei was not seen, but 
13 indicates 1 of the chromatin in the cells shown in jigs. 12 and 
Nally reach Sey ape preparing for division. The nuclei 
of the eng an extraordinarily large size, and far exceed those 
but the; -sPerm-cells. They are probably finally disorganized, 
ion ma ng history was not followed. Whether fragmenta- 
’@S In the large multinucleate antipodal cells of some 
