159 



IKiiili Christ Polypodium binerve Hooker, Syn. Pil. I, p. 17"), may also belong 

 here. They have a strong apparent, but merely apparent, affinity to I'rosaptia, 

 especially to P. contiyua monosora, which likewise has a single apical immersed 

 sorus in each pinna. But this position of the sorus has been attained in entirely 

 different ways. The sorus of P. contigua was originally dorsal and deeply im- 

 mersed; its cavity now opens toward the margin instead of dorsally. The form 

 with single apical sori, though sometimes a feature of immature plants, is 

 certainly derived from that with many marginal sori. The ancestors of Acro- 

 sorus were Polypodia with superficial dorsal sori, one on each pinna, more or 

 less protected by the dorsal concavity of the pinna, or the folding upward and 

 backward of its basiscopic half, as now known in P. trichomanoidcs, P. cucullatum, 

 P. strcptophyllum, and P. yracillimum. Acrosorus is unquestionably an offshoot 

 from this group of Polypodium. It is related to Prosaptia only through the 

 remote common ancestry of this group and that of P. obliquatum. Combining 

 I'rosaptia and Acrosorus would violate the most fundamental principle of sys- 

 tematic botany, by failing to make the classification express, as best we can, the 

 real affinities of the plants. The remaining alternatives are the enlargement 

 of the already cumbrous Polypodium to include these plants, and the establish- 

 ment of a new genus. Neither Prosaptia nor Acrosorus has any near affinity to 

 Davallia. 



Acrosorus exaltata Copel. (Table 15.) 



Davallia exaltata Copel., in Perk. Fragmenta PI. Phil., p. 180, 1906; 

 Polypodiacese of the Phil., p. 52, 1905. 

 Acrosorus frederici et pauli (Christ). 



Davallia frederici et pauli Christ in Pil. Sarasin. II, p. 124, Tab. I; 

 Farnflora v. Celebes, p. 94, Tab. 14, 1904, Farnkr. d. Erde, p. 30G. 



Polypodium frederici et pauli Christ in Farnflora v. Celebes, II, p. 37. 



POLYPODIUM Linn. 



Polypodium dolichosorum Copeland n. sp. 



Rhizomatc late repente, 1 mm. crasso, paleis fulvis amplia ovatie %-A 

 mm. longis vestito; stipite duro, fnsco-nigro, pilis rubidis vix 1 nun. 

 longis vestito vol deorsum glabro, ca. 4 cm. alto, non articulato; fronde 

 ca, 15 em. alta, 1 em. lata, utrinque attenuata, apice obtusa, integer- 

 rima, glabra, coriacea, opaea; venis plerumque 2-fnrcatis; soris obliquis, 

 oblongis, in seriam imam inter costam marginemquc inafcructis, costam 

 propioribns, paulo immersis. (Tab. 16.) 



Mindanao, Davao, 1,800 m. s. m., Copeland 1524. 



A fern related to P. australe Mett. and P. cacspitosum (Blunie) Mett., distin- 

 guished by the long rhizome, long, stout stipes and coriaceous fronds. Found 

 on the ground, but probably as much at home on trees. Many of the smaller 

 plants of the very humid forest grow indiscriminately on trees and on the ground. 

 Not a few Eupolypodia in such places have nonarticulate stipes. 



Polypodium decrescens Christ, Ann. Jard. Buitenz. II. 4: 35. 1904. (Tab. 17.) 

 Luzon, Lepanto, Bagnen, Copeland 1916. De truncis pendente, 1900 m. s. m. 

 Celebes. 

 This species is very similar to P. subsessile Baker (P. pteropus Hooker, Sp. 



Pil. 4: 192, PI. 275), of South America; but its pinnae are much closer together 



and less dilated at the base. 

 42121 2 



