1923] JURICA—UMBELLIFERAE 297 
(38), Paver (56), and SEILER (62) have noted it in their work. 
Nevertheless, it is not out of place to note that, in one exceptional 
case, all the flowers of one head of Eryngium yuccifolium developed 
two normal ovules in each ovary cavity (fig. 13). 
Megaspore and embryo sac 
By the time the ovule has reached the stage shown in fig. 17, 
the nucellus has become quite prominent, and the hypodermal 
archesporium is easily recognizable (fig. 18). This figure shows the 
megaspore mother cell nucleus in synapsis, which indicates that 
the reduction division is about to occur. The successive stages 
in the development of the megaspore, resulting in a linear row of 
four megaspores (fig. 19), as well as the destruction of the potential 
Mmegaspores, present no essential deviations from the process as 
ordinarily described, for the embryo sac develops from the innermost 
megaspore, and Sium cicuiaefolium is no exception in this case 
(figs. 15,16). The nucellus has only a single layer of cells surround- 
ing the megaspore, but the absence of tapetal cells is well com- 
pensated by the presence of a nutritive apparatus (figs. 16, 20-25) 
in the chalazal region. The nucellus undergoes but slight develop- 
ment, and then begins to break down (figs. 16, 21-25). Even in 
the development of the embryo sac there is nothing unusual. 
The megaspore nucleus divides by three successive divisions, and 
at first an eight-nucleate, and then a seven-nucleate embryo sac 
is the result. The amount of protoplasm in the developing sac 
is comparatively small, frequently resulting in the presence of very 
large vacuoles, not only in the embryo sac proper, but in the 
synergids and oosphere as well (figs. 23-25). The antipodal cells, 
three in number, can easily be seen in the embryo sac before the polar 
nuclei fuse, and generally are arranged in the form of a triangle 
(fig. 24). They soon break down, however, and only rarely can 
be distinguished at a later stage (fig. 16), that is, they are somewhat 
ephemeral, breaking down shortly before or after the fusion of the 
polar nuclei. 
Endosperm and embryo 
Shortly after double fertilization the endosperm nucleus begins 
to divide, forming an endosperm consisting of free nuclei (figs. 26, 
