8 IOWA STUDIES IN NATURAL HISTORY 
The embryo-sae at maturity is narrowly triangular in form 
(Fig. 7), the feeble antipodals occupying the narrower end. The 
egg and broad synergid cysts are anchored to the funicular side 
of the embryo-sae and are soon left far above its tip as the pro- 
toplasm pushes past the egg apparatus into the haustorium. 
The polars meet a little above the egg, flatten together some- 
what, and seem to remain in that relation until the pollen tube 
enters the ovule (Fig. 7). Proof of this is obtained from flowers 
in which only a part of the ovules have been fertilized. Inter- 
mixed with ovules containing embryos are others that failed to 
receive pollen tubes, and in these the polars are joined but not 
fused. Their union seems to be regularly completed, how- 
ever, before the sperm reaches them. 
The antipodals are never prominent and enter into early 
decline (Fig. 7). At maturity they are small and feebly stain- 
ing nuclei that occupy the tip of the embryo-sac. With the 
entrance of the aggressive endosperm nuclei into this region 
they disappear entirely, so that the antipodal haustorium, later 
developed, is wholly an endosperm structure. 
Cells of the ovary adjacent to the embryo-sac take on marked 
changes during its development and constitute the so-called 
“‘tapetum’’ of various authors. The cells elongate at right 
angles to the longer dimension of the embryo-sac, and in the 
outer part of the ovule are twice the diameter of the embryo- 
sac in length (Fig. 9). They seem to be equally prominent on 
the funicular and integument sides of the gametophyte. 
MALE GAMETOPHYTE 
The pollen grain measures 26x30 microns, and has its sur- 
face covered by a series of encrusted ridges giving it the appear- 
ance of a summer squash (Fig. 15). The microspores adhere 
in sticky masses, and in pollination by the visiting flies are 
rubbed off against the stigmatic hairs which line the inner sur- 
face of the upper lip of the stigma (Fig. 1). Upon germination 
the pollen tubes pass upward among the stigmatic hairs and 
enter the tissues of the upper lip of the stigma. From there 
they enter the back wall of the style and pass obliquely through 
it, following no fixed path until they enter the stylar canal. 
