SEED PLANTS 169 
microspore produces a rudimentary antheridium with 
two sperm-cells, much as in Cycas, but so far as known 
at present, the formation of spermatozoids is completely 
suppressed. It would not be surprising, however, if 
some trace of such structures should be discovered. 
The germination of the pollen-spore when it falls upon 
the ovule is like that of Cycas, but the pollen-tube pene- 
trates through the neck of the archegonium, and the 
sperm-nucleus is discharged directly into the egg. 
In the higher Conifers, such as the pines and firs, the 
macrosporangia are developed upon special sporophylls 
(carpels) which not infrequently are borne in the axils 
of sterile bracts. ‘The sporophylls are arranged spirally 
about the axis of a shoot, forming the familiar “ cones” 
of these trees. As in the yew, the single macrospore 
which is finally formed in the sporangium produces 
the large female gametophyte, much like that of Sela- 
ginella. The archegonia are several in number, with 
very large egg-cells, but the neck parts relatively small, 
as they are in all Gymnosperms. The sporangium is 
invested with a single integument as in the other forms 
described. 5 
The microsporangia are also borne upon special sporo- 
phylls, and are usually arranged in a cone like those 
bearing the ovules. These microsporangia or pollen- 
sacs correspond in every detail of their development 
with those of the Pteridophytes. The ripe pollen- 
spores in the pines (Fig. 42, E) and firs are provided 
with wing-like outgrowths of the outer membrane, 
which form very efficient sails by which they are more 
easily scattered by the wind. As the pollen must de- 
pend upon the wind for its distribution, the number of 
