134 BOTANICAL GAZETTE [AUGUST 
gametophyte then is made up of one prothallial cell and a naked 
mass of sperm cells, which later come to float in the slime 
produced by the disorganization of the food granules. Some- 
times at this stage the large deeply stained prothallial cell may 
be seen flattened against the endospore (jig. 97). There 
are about 128 sperm cells. The exospore splits along the three 
ridges from the apex downward, and the endospore, dilated with 
fluid, protrudes through the gap (figs. 98, 99). The sperm cells 
separate from one another, and a single spermatozoid is organ- 
ized in each. These are spirally coiled like those of Osmunda— 
two complete turns and a part of a third—but I can demon- 
strate no cilia (figs. 33, r00). Neither in appearance nor in 
movement do they resemble any bryophyte spermatozoid with 
which I am familiar, or have seen figured. The movement of 
biciliate gametes is characteristically different from that of an 
ordinary fern. These spermatozoids progress with a screw-like 
motion. The latest stages of development occur in the strobili 
after they are shed. 
MicrosporanGium.—At maturity the microsporangium wall 
consists of two layers of cells, of which the outer is divided into 
regions of thick and thin-walled cells, which enable the spor- 
angium to open lengthwise into two symmetrical valves (jig. 
62). The microspores are discharged with much force. If 
plants that have become somewhat dry are watered copiously 
and covered with a bell jar, the ripe microsporangia burst open 
and jerk back their valves, which instantly recoil and hurl the 
microspores. These may be seen, looking like red powder, 
lodged in the axils of leaves or upon any other part of the 
plant where they have chanced to fall. Of necessity the waste 
must be great. _If this is the method adopted by the plant to 
secure fertilization it may account in a measure for the extremely 
small number of sporophytes that are developed. 
S. apus grows most profusely in a neighboring locality, where 
almost daily observations have been made during the past year. 
Early in May 1900, when this work was undertaken, the strobili 
were well advanced. It was observed that if several eggs in one 
