338 The Botanical Gazette. [June, 
are smaller than the vegetative nucleus, move together into 
the tube. In a number of preparations these two nuclei were 
seen a short distance behind the vegetative nucleus near the 
place where the tube penetrates the sporangium wall. After 
entering the sporangium the tube passes obliquely downward 
and enlarges considerably. It soon becomes impossible to 
distinguish it in sections from the numerous windings of the 
Several variously developed embryo-sacs with which it inter- 
twines; and so it was not traced to the mature female prothal- 
ium. A study of the sectioned material is often made still 
more confusing by the fact that one or more of the secondary 
embryo-sacs with their free nuclei sometimes escape from 
the sporangia and grow around, up or down inside the integu- 
ment. These are however larger than the pollen-tubes. An 
attempt was made to isolate the older pollen-tubes by macer- 
ating the sporangia in 5 per cent. and 10 per cent. caustic 
potash solutions but without success. It was found that this 
method showed clearly the course of the tubes before entet- 
ing the sporangia but not farther. Some sectioned specimens 
show with little doubt that the pollen-tube usually or at least 
frequently grows down alongside the female prothallium, but 
as some of the secondary embryo-sacs with free nuclei often 
do the same thing nothing more definite was learned. 
In some cases several of the embryo-sacs develop 155 
and again the single large prothallium may appear as Seve 
in sections by reason of constrictions produced by other 1m- 
mature sacs or by pollen-tubes. 
The peculiarity of the pollen-tubes is that they do not pet 
etrate the wall of the sporangium in the immediate neighbor 
hood of the micropyle but at lateral points in the uppe 
of the sporangium. In this respect, and in the distinctly 
branched form which the tube develops, * Sequoia beats a 
least a remote resemblance to some of the so-called chala- 
ue, 
ral 
development of the secondary embryo-sacs, are characters 
*S. Nawaschin, Botanisches Centralblatt 63: 355. 1895. 
