116 ASPLENIUM EBENOIDES.—SCOTT’S SPLEENWORT. 
wiler does not mention the latter species, which probably also 
grows near the Alabama location; but the association need sug- 
gest hybridity no more than in the case of others also often found 
associated. Again, those who have experimented with them, tell 
us it is extremely difficult to produce hybrid ferns. When 
germination of the spore takes place, a small green blade called 
the prothallus is formed. On the surface of this little cups appear, 
which represent the different sexes in flowering plants, and the 
fertilizing dust, or pollen, as we should say in flowering plants, is 
ejected from the one class, and has to fall into the other. The 
chances of the fertile vesicle, or, as it is technically called, the 
archegonium, receiving fertility from any other source than its 
own prothallus, are found to be very slim indeed. Asa means 
to make it more probable, hybridists sow the spores of two 
species in immense abundance thickly together, so that when the 
prothallia develop they may be pushed up on edge, and in that 
way the antherozoids or “pollen” be more likely to be thrown 
into the receptive vesicles of the other species. One experi- 
menter reports that of millions of plants so favorably raised for 
hybridization, he yet never saw but two undoubted hybrids. With 
this difficulty it is scarcely within the probabilities that a hybrid 
between the Walking and the Ebony ferns should appear in so 
many different and such widely separated locations. 
EXPLANATIONS OF THE PLATE.—t. Plant of natural size from Miss Tutwiler’s location. 1. 
2. 3. Various enlarged sections of pinnules from different parts of the plant,—showing 
variations in the venation. 
