sac, near the antipodal end, which he says takes place | ‘ 
S origin. He makes no mention of any wall cutting i 
oe ee 
216 BOTANICAL GAZETTE [mance 
At this time, the upper polar nucleus (fig. 8) beginsa migration — 
toward the antipodal end of the sac, at the same time increasing 
somewhat in size, so that it has very much the appearance of an 
endosperm nucleus. This migration continues until the nucleus 
reaches the region of the antipodal nucleus (fig. 9), though 1 : 
fusion takes place, for the latter can be seen in all but the very 
latest stages of the embryo sac and embryo. The upper polat 
nucleus, when it has approached the antipodal end of the sae, 
divides transversely (fig. ro). The lower daughter nucleus 
remains in the position of its formation, being cut off by a wall, : 
across the sac (figs. rz-12), and: forming a large cell that does 
not divide further, but finally disappears through the encroach 
ment of the endosperm. In Butomus umbellatus, Marshall Ward 
says that the two polars approach the middle of the sac, where 
they fuse, forming a definitive nucleus, and leaving — 
antipodal nucleus. In Sagittaria, Schaffner shows a $ 
division of a large nucleus, and formation of a wall across 
_ fusion of the polar nuclei; and he states that freq atly 
nucleus of the cell cut off toward the lower end of t 
_ to form two or three, when the embryo is in abou an 
2 celled stage. Campbell describes a similar large nu 
Naias and Zannichellia, but does not state definitely ' what 
e rest of the endosperm, but suggests that it ma: be 
S polar nucleus. Such cannot possibly be the origin © 
“3 —s) walls are formed, ace os 
_ Limnocharis, because there is no lower polar formee- . 
= Says that the nucleus resembles the suspensor © ee 
that the nucleus stains more readily than the susp 
oS The upper daughter nucleus travels back 
_ appa ratus (figs. 11, 72), and by its further di 
_ endosper m. Atan early stage the endosperm col 
_ 4 single layer of granular protoplasm lining the sac 
embedded free nuclei, as in Naias and Zanniche lia; ‘ 
