256 Field, Forest, and Wayside Flowers 
which is attractive—but we do not yet know just 
how or why—to the spermatozoids. 
Some rainy day or dewy night, when the under 
surface of the prothallus is wet, the active little 
swimmers approach the open neck of the arche- 
gonium, and are lured into it. And down in the 
rounded part of the flask they find the ‘‘ affinity ”’ 
which they have been unconsciously seeking, a 
naked globe of colorless jelly known as the ‘‘ oo- 
sphere.’’ One spermatozoid enters the oosphere, 
and mingles with it, and with this act of fusion 
the life-purpose of the prothallus is accomplished. 
The now fertilized oosphere surrounds itself with 
‘ Le 
a delicate membrane, and becomes the “‘ oospore. 
So again in the life-history of the fern we have 
come around to the single ‘‘ cell’’ or globe of pro- 
toplasm from which we can trace the development 
of every living organism. 
From the first globe—the fern-spore—creative 
Nature made the tiny heart-shaped prothallus. 
From the second globe,—the oospore,—she will 
make the perfect fern. 
A prothallus may form a number of archegonia 
before a spermotozoid finds its way into any one 
of them. But as soon as an archegonium is fer- 
tilized no new ones appear, and the remaining life 
