riEMESTHEUM THELYPTEIIIS. 



123 



MARSH FERN, {one-ninth the natural sine). 



(i\Kx^dm, 



Genus. — Hemestheum. Midvein of pinnules distinct ; late- 

 ral veins alternate, always forked soon after leaving the mid- 

 vein, and both branches runniag in parallel lines to the 

 margin : each bears a cluster of capsules near the fork, and 

 these beiag equidistant from the midvein and the margin, form 

 two continuous series, which are concealed by the convolute 

 margin of the pinnule : involucre minute, indistinct, subreni- 

 form, evanescent : each first upper and first lower pinnule 



