Igtt] SHREVE—JAMAICAN HYMENOPHYLLACEAE 193 
is the commonest filmy fern in Jamaica, and, with the exception of 
the hairy forms to be mentioned, it is the most capable of resisting 
desiccation of any of the species. On losing water its pinnae curl 
downward and the midrib itself then curls, so that the whole leaf 
tends to close into a form resembling the circinate shape of a 
young leaf. Hymenophyllum fucoides and H. catherinae have also 
characteristic modes of curling up on becoming relatively dry. 
The writer has seen the rain forest on exceptionally bright days, 
when the humidity had fallen to 60 per cent, when every plant 
of these three species was curled in a marked degree. The curling 
is not at all in such a manner as serves to protect any part of the 
leaf from further desiccation. 
The three pendant hairy forms Hymenophyllum sericeum, H. 
lanatum, and H. hirsutum are the most resistant to drying and 
insolation of any of the filmy ferns. Their pendant habit confines 
them to the sides or bottoms of logs and leaning trunks, and they 
are most flourishing just beneath large clumps of mosses and he- 
patics, which serve as reservoirs from which supplies of water may 
be secured for several days after a rain. Hymenophyllum sericeum 
is not common in the topmost limbs of trees, probably through the 
lack of the moss substratum, but it grows in situations where it 
Must often be subjected to two or three hours of sunshine on clear 
days, and it sometimes occurs as much as 12 m. above the ground 
in slope forest (figs. 3, 4). As the leaves grow the old pinnae die 
off, so that it is not an uncommon thing to find a naked rachis 
39-40 cm. long with a dozen pairs of young pinnae at the tip. 
There are two hairy pendant species of 7richomanes, T. lucens and 
T’. crinitum, but they are not at all resistant to desiccation. They 
are almost confined to the under sides of rotting logs, where they 
are rooted in the log itself and sheltered from rain and the drip 
ftom foliage. The writer has seldom seen wet leaves in nature in 
either of these species, both of which have a metallic gray-green 
color. Their physiology has not been investigated. 
Physiology 
Roor-azsorprion.—In order to test the ability of the various 
‘pecies of Hymenophyllaceae to secure by root-absorption all the 
