2g8 
KEYS TO THE FERNS OF BORNEO 
KEY TO THE FAMILIES OP BORNEAN PERNS. 
a. Sporangia large, without an annulus, 
each derived from plural cells Eusporangiatse. 
b. Stipules wanting, sori on specialized 
segments without lamina, prothallium 
tuberous i. Ophioglossace.e. 
Stipules present, sori on normal seg¬ 
ments of frond 2. MARATTiACEai. 
a 1. Sporangia smaller, each derived from 
one cell 
b. Spores uniform, leaves not cruciform 
c. Annulus horizontal, incomplete or 
rudimentary 
c 1 . Annulus surrounding the apex of the 
sporangium 
c 2. Annulus complete, more or less 
horizontal, around the middle of the 
sporangium. 
d. Sori round, dorsal, exindusiate 
d l . Sporangia on free tips of veins, 
surrounded by a tubular or equally 
two lipped involucre (indusium) 
c 3 . Annulus subvertical and complete, 
or vertical and interrupted by the 
stalk of the sporangium 
C4. Annulus vertical, decidedly incom¬ 
plete 
b 1. Spores of two kinds, large and small 
Leaves cruciform 
Leptosporangiatse. 
FILICES. 
3. OSMUNDACE. 5 . 
4. SCHIZ.EACE.E. 
5. Gleicheniace.e. 
6. Hymenophyllace^e.. 
7. PoLYPODIACEJE. 
8. Parkeriace^e. 
HYDROPTERIDES. 
9. MARSILEACEat. 
