676 UnpERWOOD: FERNS OF THE PHILIPPINES 
slight representation in the island flora. The several genera may 
be distinguished as follows: 
1. Sporangia attached to the under surface of marginal lobes; leafstalks black and 
shining. ADIANTUM. 
Sporangia rising from a marginal vein-like receptacle. 2. 
Sporangia rising from the ends of unconnected veins ; sori continuous or interrupted. 5. 
2. Indusium double, the inner membranous, extrorse. 3- 
Indusium single. + 
3. Leafstalks with several fibrovascular bundles. PTERIDIUM. 
Leafstalks with a single semicircular fibrovascular bundle. PAESIA. 
4. Spores sphaero-tetrahedral. PTERIS.* 
Spores bilateral ; leaves glaucous with auricled pinnae. HISTIOPTERIS. 
5. Leaves uniform, 6. 
Leaves dimorphous. 8. 
6. Indusium continuous; stems black, polished. DoRYOPTERIS. 
Indusium interrupted. : be 
Indusium wanting. NOTHOLAENA. 
7. Sori distant in sinuses of leaf. Hypo.epis. 
Sori crowded, more or less confluent. CHEILANTHES. 
8. Leaves simply pinnate, PLAGIOGYRIA. 
Leaves decompound. ONYCHIUM. f 
Of the above genera Paesia and Histiopteris are each repre- 
sented by a single Philippine species, Onychium, Pteridium, Dory- 
opteris, Hypolepis, and Notholaena by two each, and Cheilanthes 
and Plagiogyria by three each. Adiantum has six representatives, 
of which one and possibly two are introduced species, while over 
twenty species of Preris have been reported. The latter genus, 
and particularly its larger species, require careful field study ; the 
peculiar tripartite branching of the larger species should be spe- 
cially noted. 
Tribe 6. Asplenieae 
Next to the Polypodieae this tribe forms the most extensive 
portion of the Philippine fern flora; the thirteen genera repre- 
sented may be distinguished as follows : 
I. Sori parallel to the midribs. z 
Sori oblique to the midribs. a 
* We have taken up Pteris as treated by Diels, /. ¢., including species with foes: 
free and anastomosing veins. These have been separated by Pres! and others, a0\ 
further study will doubtless prove that they were correct. 
t Diels following Prantl unites this with Cryptogramma, for which we can see RO 
valid reason. 
