390 
KEYS TO THE FERNS OF BORNEO 
56. ACROSTICHUM Linn/eus. 
A. AUREUM L. 
Common in somewhat brackish swamps. 
Pantropical. 
57. POLYPODIUM Linnaeus. 
Key to the Subgenera. 
a. Veins free 
a*. Veins enclosing areolae in regular rows, 
each with an excurrent veinlet 
rt2. Veins anastomosing less regularly, or with 
irregular free included veinlets. 
b. Fronds not pinnatifid with separately 
deciduous segments. 
c. Rhizome not hollow and inhabited 
by ants. 
d. Sori not single and linear between 
the main veins, or fronds not nearly 
entire 
Sori single and linear between the 
main veins, frond entire or nearly so 
c i. Rhizome hollow and inhabited by ants 
b i. Fronds pinnatifid, segments deciduous 
from costa 
1. EU POLY PODIUM. 
2. GONIOPHLEBIUM . 
3. PHYMATODES. 
4. SELLIGUEA. 
5. MYRMECOPHILA. 
6. DRYNARIOPSIS. 
Subgenus I. EUPOLYPODIUM. 
Section i. Leaves simple and undivided 
a. Fronds not borne on hairy stipes. 
b. Frond more than 100 times as long as 
wide. 
c. Frond about as thick as wide 
U. Frond dorsi-ventrally flattened 
b 1 . Frond roundish or broadly oblong 
b*. Frond form intermediate between the 
preceding. 
c. ^Sessile or nearly so; small ferns. 
d. Sori round 
d*. Sori oblong. 
e. Frond 5 mm. or more wide, sub- 
coriaceous 
ei. Frond narrower and thinner 
c 1 . Stipe 1 cm. or more long. 
d. Frond under 6 cm. long 
di. Frond over 15 cm. long 
at. Fronds borne on hairy stipes. 
“ Grammitis.” 
1. P. bisulcatum. 
2. P. setaceum. 
7. P. flabellivenium. 
3. P. vittarnfolium, 
4. P. malaicum. 
5. P. Maxwellii. 
6. P. hinabaluense. 
8. P. fasciatuvi. 
