No. 430.] THE EMBRYO SAC OF ANGIOSPERMS. 779 
which usually become surrounded by definite cell membranes, 
form the three antipodal cells. The polar nuclei, either before 
or after fertilization, fuse to form the primary endosperm nucleus. 
The most marked deviations from the typical development 
observed by the earlier investigators were an increase in the 
number of archesporial cells (Rosa sp., Helleborus, etc.) and an 
increase in the number of antipodal cells. Of the latter varia- 
tions the most marked examples were various species of grasses, 
first noted by Hofmeister. Further examples of both of these 








? 
aD 




C, 
Wis na 
Hi ds 
| LH 
SERES 
P bl 
(es 

Fic. 2. — Ovules of Arisema triphyllum: A, B, in longitudinal section; C, D, transverse 
sections of the nucellus; the archesporial cells are shaded. 
deviations from the type have been recorded by later investi- 
gators, and other modifications, not hitherto observed, have 
been discovered. 
The departures from what may be termed the typical devel- 
opment may be referred to several categories. Besides those 
already referred to, these are three in number: (1) an increase 
in the number of nuclei before fertilization has taken place ; 
(2) peculiarities in the formation of the endosperm ; (3) the 
so-called double fertilization. 
The increased number of archesporial cells observed by 
Strasburger in Rosa livida, Helleborus cupreus, and other form Et 
has been found to occur in a considerable number of forms. 
lGoebel Outlines of Morphology, etc. 
