ON THE SPORES OF CERTAIN CONIFERAE. 
We C. CeocER: 
(WITH TWENTY-FOUR FIGURES) 
THE POLLEN GRAIN.—There is much greater diversity in the male 
gametophyte of gymnosperms than of angiosperms. Such forms as 
Thuja, Taxodium, and Taxus have this structure so much reduced 
_as closely to resemble, in the number of cells formed, the pollen 
grains of the flowering plants. Others, as Ginkgo, Pinus, and Podo- 
carpus, contain, sooner or later, as many as six nuclei in the pollen 
grain and tube. In my paper on Taxodium I have summarized the 
present knowledge on this point in gymnosperms, and it is seen that 
much yet remains to be done before the structure of the pollen tube 
is understood in all genera. 
During the spring of 1902, while in Bonn, I examined almos 
daily the maturing pollen grains of a number of conifers, and followed 
them to the time of shedding. This was for the purpose of settling 
the point as to whether it were possible that a sterile prothallial ct 
or cells might be cut off early in development and, becoming disor- 
ganized, be overlooked in the ripe grain. 
In the following species it was found that no division whatel® 
occurred in the pollen grains while they were in the sporangiu 
and that they were shed in the one-celled stage: Cupressus Govemans 
C. macrocarpa, C. Benthamiana, Taxus baccata and vats. open : 
jastigiata, cuspidata, and adpressa, Juniperus sphaerica, J : ee 
In Cupressus sempervirens, pollen from a tree growing ™ tat 
warm-house showed a division while still in the pot 
this variation from the rule in this genus probably resulted from - 
in the dehiscence of the sporangium, caused by the unnat acct 
ditions. It could easily be seen that dehiscence did not ; 
promptly and in some cases was only partial. Pollen ee is 
C. Benthamiana placed in sugar solution divided in 4 few 
about a week. ‘ust 
In the following species there was one division of the pcs 
206 
