Campbell . — The Embryo-Sac of Peperomia. 107 
shown, are the hotnologues of the two polar nuclei of the 
ordinary Angiosperms. 
The remaining nuclei, which lie close to the wall of the 
embryo-sac, are more or less flattened, and subsequently 
develop a cell- wall about the deeply stained cytoplasm, form- 
ing a lenticular cell which projects into the cavity of the 
embryo-sac (Figs. 5, 7, x). 
The Pollen, 
The small, globular pollen-spores (Fig. 8) have a roughened 
membrane, and contain when ripe two relatively large nuclei. 
The larger of these, which stains much less deeply than the 
other, and has a more conspicuous nucleolus, is the vegetative 
nucleus. The other, which stains very strongly, is the genera- 
tive nucleus. In no case was a division of the latter observed 
in the ungerminated spore. 
Pollination is effected some time before the embryo-sac is 
mature. Nothing unusual was noted in regard to the growth 
of the pollen-tube through the pistil. It penetrates as usual 
through the micropyle, and on reaching the apex of the 
nucellus pushes apart the large epidermal cells, and then 
crowds between the tapetal cells, which are not, however, 
destroyed, and finally comes into direct contact with the egg 
( Fi g- 3)- 
Pollination. 
In one case (Fig. 4) two similar, deeply stained nuclei were 
seen within the end of the pollen-tube which had just reached 
the embryo-sac. These were, with little question, the two 
generative nuclei, which were the result of the division of 
the single generative nucleus of the ripe pollen-spore. The 
vegetative nucleus of the pollen-spore could not be certainly 
detected in any instance within the pollen-tube, although in 
one case a body that looked as if it might be the dis- 
organized remains of a nucleus was seen within the tube, 
above the generative nuclei. 
