PHILIPPINE FERNS, IV. 
PROSAPTIA Presl. 
115 
Prosaptia linearis Copel. sp. nov. 
Species distinctissima ; rhizomate subrepente, ad apicem paleis angustis 
canceliatis atro-fuscis ciliatis vestito; stipitibus confertis, exarticu] atis, 
brevibus; fronde usque ad 40 cm longa, circiter 16 mm lata, pinnata, rhachi 
tenue, nigra, ubique glabra ; pinnis late adnatis non confluentibus, acutis, 
integris, coriaceis, inferioribus sensim in dentes diminutis ; soro in pinna 
quaque uno, costa orto, profunde immerso, apud vel ad marginem acrosco- 
picum aperto, annulo inaequale ciliato circumdato. 
Luzon, Province of Benguet, Mount Pulog, For. Bur. 16303 Curran, Merritt, 
& Zschokke, on mossy trees, altitude 2,700 m, Copeland. 
A bizarre fern, resembling. Loxoscaphe in the appearance of the fruit. The 
solitary sori and the very narrow fronds strongly suggest Acrosor-us, but the 
origin of the protection of the sorus is very essentially different. Small fronds 
are so similar to those of Polypodium decorum that I at first regarded it as 
derived from that species, and therefore to be treated as genetically new, rather 
than included in Prosaptia. However the palese are like those of Prosaptia, 
while those of Polypodium decorum have thinner k walls and are not ciliate. 
The tip of the pinna is produced as a sharp point beyond the sorus, and bent 
toward the tip of the frond. As the fronds are pendent these tips serve to 
drain off water and protect the sori from wetting. The ecological significance 
of the movement of the sori to the margin, found independently in many groups 
of ferns, I have before interpreted ; as also the value of the rim, and the circle 
of hairs around the sori. 
