April, 1905.] 
Staphylea trifoliata. 
321 
The embryo sac widens slightly as it develops to the eight 
celled stage (Figs. 11-13) and the nuclei arrange themselves in 
the normal positions, three at the top becoming the synergidae 
and egg cell, the three lowest settle into a pocket and gradually 
disintegrate while the two polar nuclei approach each other and 
hnally come to rest in contact. 
Sections which showed the archesporial cells showed the 
microspores fully developed and the tapetal layer already break- 
ing down (Fig. 14). Older flowers gave thick-walled pollen 
grains having two nuclei, the pollen tube nucleus and the gen- 
erative nucleus. This pollen grain (Fig. 15) resembles those of 
Acer rubrum (Mottier) and Staj)hylea pinnata (Strasburger). 
The latter reports the division of the generative cell into the two 
sperm cells after the formation of the pollen tube. The gen- 
erative cell stains quite dark and is apparently enclosed by a 
wall, making the entire pollen grain very similar to that of the 
staminate flower of Acer rubrum. 
In the formation of the definitive nucleus two polars usually 
unite (Fig. 13) but in several instances three exactly similar 
nuclei were found fusing (Fig. 17). In one case, however, there 
was found what seems to be the union of one of the sperm nuclei 
with the polars (Fig. Ifl). This third nucleus is surrounded by a 
small amount of cyto])lasm which stains distinctly darker than 
that of the polars and the nucleus contains a single small dark 
nucleolus. 
After fertilization the embryo sac enlarges, the formation of 
endos])erm occurs rapidly and the ovule increases greatly in size. 
The endosperm forms a large loose single layered lining for the 
entire embryo sac before any division of the one celled embryo 
occurs. The ovules are about one-fourth the mature size before 
anything larger than a one-celled embryo is found (Fig. 18). 
The two-celled (Fig. 19), and four-celled stages (Figs. 20,21 and 
25), were found in half grown ovules. Seeds which were full size 
ljut still not too hard to section contained embryos still too 
young to show the development of the cotyledons (Figs. 22-24). 
Capsules which contained these full sized ovules had attained 
their normal bladdery inflation. The endosperm was abundant 
l)ut the nuclei had not begun the formation of walls so that the 
multinucleate cells which Strasburger finds in Staphylea pinnata 
were not ol)served. 
The synergidae have usually disa^jpeared or are completely 
obscured by the aljundant endos]jerm l>efore the one celled 
embryo divides but in a few cases traces of them were seen with 
a four-celled embryo (Fig. 20). No traces of the antipodals 
were evident after division of the endosperm nuclei became rapid. 
Division of the suspensor occurs with the formation of the 
quadrant and seems to retrogress towards the basal cell but the 
