UNDERWOOD: AMERICAN FERNS 249 
which are found in the American tropics and a considerable num- 
ber of species are widely distributed in the Old World.* The 
members of this group are distinguished by forming a single fork, 
each branch of which develops directly into a long bipinnate por- 
tion; as in the other sections the bud at the fork may develop 
into forks of the second and third orders forming an indefinite 
growth at the end of the axis. This group forms the section 
Diplopterygium of Diels. 
2. The species of the second group, which form the section 
Holopterygium of Diels, have the characteristic forking indicated 
in FIGURE I, with the segments decurrent on the nodes sometimes 
even to the primary ones. It was in this section that Sturm char- 
acterized a dozen South American species in 18 59, anda resurvey 
of the same area at the present time would probably double that 
number; this work we hope later to be able to accomplish when 
the types in European herbaria have been studied still further, for 
without this no progress is possible. Most of the West Indian 
and Mexican species have been confused with Gleichenia bifida 
and G. pubescens, both originally described from South America, 
but a study of type material has convinced me that neither of 
these species occurs in present collections north of Panama. This 
is Strictly in accord with the conclusion reached long ago by 
* Among other members of this group the following species submerged by reduc- 
tion to Synonymy, which we have studied at Kew and Berlin, we regard worthy of 
Specific recognition : _ 
Dicranopteris glauca (Thunb. ). 
Polypodium glaucum Thunb.; Houtt. Nat. Hist. 14:177. 1783. (Type from 
Japan. ) 
Dicranopteris glabra (Brack. ). 
Mertensia glabra Brack. Wilkes Expl. Exp. 16:292. 1854. (Type from 
Hawaii, 
Dicranopteris gigantea (Wall. ). 
Gleichenia gigantea Wall. Cat. n. 157. 1827 (women nudum) ; nee 
Fil. r:5. pf. 9 4 1844. (Type from Nepal.) 
Dicranopteris longissima (Blume). 
Gleichenia longissima Blume, Enum, PI, Jav. 250. 1828. (Type from Java.) 
Dicranopteris arachnoides (Hassk.). 
F Mertensta arachnoides Hassk. Jour. Bot. Hook. 7 : 322. 1855. (Type from 
ava, ) 
It is more than likely that other species of this section are confused in European 
herbaria, particularly with D. gigantea and D, arachnoides of the above list. 
