OPHIOGLOSSUM. 137 



venules branch out, these being usually forked, and both 

 branches bearing a sorus half-way between the margin and 

 the midvein. The sori, which are thus pretty numerous, 

 often become confluent, and are partially concealed by the 

 bent-back margin. The indusium, or cover of the spore- 

 cases, is in this species small and thin, and is soon thrown 

 off, and lost. 



The Marsh Pern has a wide geographical range, and in 

 England and Wales occurs in numerous localities ; in Scot- 

 land and Ireland it is rather uncommon. 



Not a very attractive species for cultivation. It has 

 been severally referred, under the individual name of TJiely- 

 pteris, to the families of Aspidiwm, Poly podium, Acrostichum, 

 and Polystic/mm, by various botanical writers. 



Genus XVII. OPHIOGLOSSUM, Linnaus. 



THIS is very nearly related to the Moouwort, though at first 

 sight having a very different aspect. The points in which 

 it agrees, are, that the parts are folded up straight in the 

 incipient state, and the fronds are two-branched, one branch 

 being leafy, the other fertile. OpJiwglossum differs from 



