49 
the very moist rain forest and mossy forest, where the rhizome and roots 
are imbedded in enough other vegetation to be situated as if they were 
in the soil itself, articulations cease to be necessary, and their disuse and 
eventual disappearance can be observed, usually in ferns with small 
fronds, in many different groups of species: In the P. cucullatum group 
and in Acrosorus ; in P. pediculatum and P. macrum, with many artic- 
ulate relatives; in P. caespitosum and some other species of “Gram- 
mitis;” and in the Panay species, P. Yoderi 24 but not in P. tenuisectum. 
On the other hand, a Luzon Phymatodes, P. Proteus, growing among 
rocks on arid ground, has articulate pinnae as well as stipes. Loxo- 
gramme is probably an offshoot of Eu-Polypodium, which has developed 
a decidedly xerophytic structure with or after the loss of articulations. 
Of the San Eamon Aciirostichece , two are terrestrial and nonarticulate, 
the other is high-scandent' with articulate pinnae. 
RHIZOME. 
The stems of Polypodiacece are moderately modified in adaptation 
to a wide range of conditions — more modified and more variously 
so than one might imagine from text-book comparisons with Equi- 
setum and the Lycopodinece. The most primitive form of fern stem 
is probably a short, erect one such as is observed in Aspidium, Diplazium 
and Pteris. This may be subterranean, or barely superficial, or, in damp 
and darker places, may rise into the air, as is the case in -most of the 
large Diplazia, in Callipteris esculenta, and notably in the huge variety 
of Aspidium leuzeanum. Blechnum Fraseri, of Luzon 25 and New Zea- 
land, is remarkable among Philippine Polypodiacece for its tall and 
graceful stem. On trunks deeply covered with vegetation, some small 
ferns have stems standing out radially, with a dense, apical tuft of 
small fronds. Among these are Viltaria minor, and all the Polypodia 
with nonarticulate stipes. A large number of ferns lift the fronds 
above competition with their terrestrial neighbors by assuming the scan- 
dent habit. Such are N ephrodium 1712, all scandent species of Lepto- 
clnilus, Arthropteris, Nephrolepis volubilis, all scandent Lindsay ce except 
L. gracilis, Asplenium epiphyticum; Lomagramma, and Stenochlaeria. 
The majority of these maintain their connection with the ground, but 
are still, if we classify all ferns as either terrestrial or epiphytic, rather 
to be regarded as belonging to the latter class, because of their exposure. 
Numerous other ferns keep to the ground or to their original aerial 
support, but remove their leaves from competition with one another by 
a creeping habit and by bearing them at considerable intervals. Neither 
the geotropism of the stem, determining whether it shall be prostrate 
24 This Journal (1906), 1: Suppl. 161. 
25 Christ: Bull. Herb. Boissier (1898), 7, 149. PL 6. It is usually more 
slender than this figure shows. 
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