1901] SPORANGIA AND GAMETOPHYTES OF SELAGINELLA 131 
also disappears (with a possible exception noted hereafter), 
and the egg lies free in the venter. There is a large receptive 
spot on the oosphere, and its nucleus is not centrally placed 
( fig. 33). I have never seen more than five archegonia in a 
single gametophyte. 
FERTILIZATION.—Not only are the archegonia formed in the 
unshed spores, but frequently, at least, fertilization and the early 
phases of the sporophyte development take place while the 
sporangium with its prothallus are still in the strobilus. The 
strobili cease to grow, fade, and may separate from the plant 
before fertilization, but the spores do not fall from the spo- 
rangium. It was not until I had collected from the soil several 
hundred spores which had been shed, with the expectation of 
finding fertilization stages, that I thought to examine the with- 
ered strobili. Almost without exception in these I found 
embryos, whereas im no case have I found any evidence of fer- 
tilization in the spores that are shed. 
FURTHER DEVELOPMENT OF THE MEGASPORANGIUM.— The 
glandular tapetum is very active until the megaspores have 
stored their maximum amount of nutriment for the growth of 
the embryo. At this stage they quite fill the sporangium cavity, 
which in consequence has assumed a four-lobed appearance. 
The tapetum then declines in importance. Its cells collapse 
and form a pavement-like layer. The outer layer of wall cells 
becomes greatly modified. In section it appears precisely like 
a similar section of the annulus of a leptosporangiate fern (jig. 
52). Four areas of the larger thick-walled cells, corresponding 
to the protuberances caused by the spores lying within, are 
separated from one another by narrow strips of small cells with 
thin walls. The latter are the lines of dehiscence. The spo- 
rangium splits into two valves along these lines, but the halves 
do not separate so widely as to allow fertile spores to escape. 
Apparently they may open and close more than once. The 
Sporangium appears fresh and active, and its wall contains 
chlorophyll until after fertilization has occurred. With the 
decline of the tapetum the lower stratum of the wall becomes 
