at ee 
ia 
1904] COKER—SPORES OF CONIFERAE. 207 
before shedding: Chamaecyparis Lawsoniana pendula, C. sphaer- 
oidea, C. chinensis, C. obtusa, C. pisijera, Callitris sp., Cryptomeria 
japonica and var., Thuja orientalis. 
The fate of these pollen cells was not followed further, but the 
appearance of the small cell cut off before shedding is quite unlike 
that of a prothallial cell, and bears every 
resemblance to the single (generative) cell 
cut off at the same time in Taxodium, where 
certainly no prothallial cell is formed.  Fur- 
thermore, in all cases where prothallial 
cells are known to occur, they are produced 
while still in the sporangium, and the divisions 
that cut them off are immediately followed 
by another which gives.rise to the generative 
cell. It is hardly to be doubted, therefore, 
that no prothallial cell is formed at any time 
in the species above mentioned. 
Jn jig. 1 is shown the mature pollen grain of Thuja orientalis, the 
She hot being drawn. The generative cell is of the usual structure 
and is sharply separated from the rest of the contents. Its nucleus is 
as usual more dense than the tube nucleus. In fig. 2 the pollen 
grain of Cupressus sempervirens is represented in division, while in 
Bi : _ division is completed. In this last figure a few starch grains 
own. In most cases the generative cell is free from starch even 
Fic. 1. Thuja orientalis; 
pollen grain ready to shed. 
I 
eet: “espa sempervirens; fig. 2, pollen grain in division; fig. 3, 
Ing; figs. 4 and 5, abnormal pollen grains. X 750. 
in pollen where 
Scattered grains 
Bt <eie that the above results confirm to a large extent 
ER'S observations on mature pollen. He finds' that in 
Verhalten des Pollens, etc. 1892. 
it is abundant, but here (fig. 3) it also contains a few 
* Ueber das 
