26 FERNS OF KENTUCKY. 
The general characteristics of these sub-orders, with the 
addition of Hymenophyllacez, which, at the time Prof. 
Eaton wrote, was supposed to be unrepresented in this 
country, can be -better shown by figures representing the 
different forms of the sporangia, upon which these divisions 
are based: 
POLYPODIACE®.—Sporangia with a vertical 
(¢. e. longitudinal), incomplete, many -jointed 
ring, and therefore splitting transversely. The 
sori either cover the surfaces and veins of both 
sides of the leaf, or are confined to one side 
alone; are either distributed along the whole 
course of the veins, or are terminal on a vein 
or at a fork; are either naked or covered by 
an indusium. (Fig. 1.) 

Fig. 1. 
HyMENOPHYLLACE#. — Sporangia with an oblique or 
transverse complete ring, opening by a longitudinal slit; 
they are formed on a prolongation of the fertile veins, pro- 
jecting beyond the margin, and are surrounded by an urn- 
shaped indusium. The 
fertile end of the veins of 
the leaf projecting beyond 
its margin, or the columel- 
la, elongates by intercallary 
growth, and the newly- 
formed sporangia are, in a 
corresponding manner, produced in a basipetal succession. 
They are arranged on a spiral line on the columella. The 
sessile sporangia are biconvex, and are attached to the col- 
umella by one of their convex surfaces (Sachs). (Fig. 2.) 
See also Plate XLVII. 

Profile view. Fig. 2. Front view. 
