GENERA OF FERNS. 383 
rachis. Veins of the fertile spicula pinnate ; venules arcuate 
bearing the sporangia on their superior side. 
Examp. 1. L. flexuosum, Sw. (L. circinatum, Sw. L. longi- 
folium, Sw. L. dichotomum, Sw. L. pedatum, Sw. 2. L. scan- 
dens, Sw. (L. volubile, Sw. L. hastatum, Sw. L. pinnatifidum, 
Sw.) 3. L. Japonicum, Sw. 4. L. palmatum, Sw. 
Iilust. Hook. et Bauer gen. fil. t. 28, Hook. et Grev, ic. fil. 
$. 153. 
Obs. The peculiarly scandent and permanent character of 
the fronds of this genus readily distinguishes its species 
from all other ferns; they are found chiefly within or near 
the tropics, the same kinds being common to both hemis- 
pheres ; for after a careful examination of numerous speci- 
mens, I can detect no permanent character, whereby to 
distinguish the common Lygodium volubile of America from 
the also common Lygodium scandens of Asia. It is evident 
to me that many species, described as distinct by authors, are 
only variations of a very few species ; the more or less sterile 
or fertile state of the pinne and other circumstances often pre- 
senting such discrepancies of form, on the same plant, at the 
same time or at different periods of its growth, that viewing 
these forms separately there is little or no difficulty in con- 
sidering them so many distinct species. Sprengel enume- 
rates twenty-three species, which, according to my view, 
may be reduced to six or eight. If such be not the case, and 
allowing every deviation in form of this genus to be species, 
then I see no limits as to number, and the impossibility and 
uselessness of trying to give them distinct specific characters 
is to me a reason for considering the species to be few. 
130. Lyaopicryon, J. Sm. 
(Lygodii sp. Schk. Hydroglossi sp. Willd.) 
Fertile appendices marginal, forming numerous spicule, 
composed of two rows of indusiate imbricate cysts ; each con- 
