164 BOTANICAL GAZETTE [AUGUST 
in all of these cases no cytoplasm could be detected in association 
with the male nuclei, and also that in all views of these male nuclei 
one of them appears larger than the other, the larger one slightly 
vermiform. It remains to determine whether this apparent dif- 
ference is real or whether in each case one of the nuclei is seen from 
the end. In the embryo sac section it seems probable that the 
smaller appearing one is the one likely to fertilize the egg. 
Summary 
. The style of Iris versicolor is traversed by a longitudinal 
groove through which the pollen tube grows. 
2. It is possible to remove pollen tubes from style and stigma 
and to grow pollen tubes in nutrient solutions. 
_ 3. Measurements indicate that there i is an accelerated rate of 
growth of pollen tubes. 
4. Pollen tubes may branch or a grain may produce two tubes. 
_ §. The generative cell is an elongated, somewhat pointed cell, 
— tured precede the tube nucleus from the tube. 
usuall y Occurs: aiter the penera- 
2 ed 
tv cl has entered the tube. 
4. The male nuclei may leave the ecmative cytoplasm, and 
a been eee a a 
ae The male nuclei were serve ‘ 
ed in the embryo sac 79 hours : 
2 after pollination. oes oy 
writer is in debted to 5 Proke fessor oH. D. Dexswone of Beloit oe 
| College for suggestion which led to aking of this inves- 
_ tigation. “Acknowledgments | are = ~ Professor ae M. 
2 Courter and Dr. CHARLES Tt. 
‘the p tl 
