352 BOTANICAL GAZETTE. 
soon undergoes disorganization. I have seen this nucleus in 
various stages of destruction. The generative nucleus passes 
later into tube; indeed it is usually among the last of the con- 
tents to leave the spore. Iam not able-to say whether or not it 
divides; presumably it does,’ though I have seen but one such 
nucleus. 
When the pollen tubes are emitted on the stigma they some- 
times pass straight and sometimes after turning upon themselves 
downwards between, and not into, the bases of the papille (jig. 14). 
The conducting tissue tuns close beneath the stigmatic surfaces. 
In this tissue I have traced the tubes for several millimeters. 
The pollen tubes penetrate the strands of conducting tissue and 
do not enter the canal of the style. A short distance behind the 
es of the tubes cellulose plugs are successively formed (fig. 15). 
hese plugs, which have sometimes considerable length, are very 
prominent objects in longitudinal sections of the style or when 
the conducting tissue is teased with needles. The latter method 
permits one to trace the tubes for long distances. The pollen 
tubes pass down the style and follow the placente. When they 
emerge from a placenta they either enter the nearest micropyle at 
once or pass further, adhering very closely to the surface of the 
placenta. 
I have detected the pollen tubes in a number of micropyles. 
The difficulty of tracing their further course is greatly enhanced 
by the opacity of the ovules and the consequent necessity of 
adopting the section method, as hereafter explained. I have been 
fortunate enough to find one specimen in which the pollen tube 
had entered the micropyle and penetrated to the synergide 
(fig. 16). In this specimen fertilization had taken place. Une 
ot the synergide at least (I could not see the other) had become 
disorganized and there were two nuclei in the oosphere. 
not certain that these were the male and female pronuclei, though 
they may have been. I am rather inclined to think from t 
considerable elongation of the oosphere that the embryonal nu- 
cleus had just divided preparatory to the formation of the first 
two cells of the suspensor. After fertilization the embryo-5 
enlarges greatly, particularly in its middle third, and the forma- 
tion of endosperm proceeds at once and rapidly. : f 
he main points established regarding the fertilization © 
Campanula Americana are these : 
The tapetal cells of the anther and ovule are unusually larg® 
Sear ner ET ci RTO EER eC Ser Get 
7Strasburger, 1. ¢., p. 15, stat ivis I have not yet assured 
myself that it takes bd. os isin pn bared such division is the rule. 
