220 Y app. — Two Malayan ‘ Myrmecophilous ’ Ferns . 
change, and which yet assimilates, there may exist a tendency 
to a state of partial asphyxiation, such as that stated by 
Devaux 1 to exist, even at normal temperatures, in the deeply 
seated tissues of many woody stems. This state of affairs, 
if it exists, would be relieved by the early breaking down 
of the aqueous tissue, resulting in the formation of extensive 
compensating air-passages. In any case, it seems probable 
that, whatever its original significance, this system of galleries, 
which penetrates to almost all parts of the rhizome, and is 
in communication with the outer air, does, to some extent 
at least, assist in the interchange of gases in the stem. More- 
over, Karsten 2 states that water applied to the layers of 
small pitted cells surrounding the galleries of P. sinuosum 
is at once sucked up by these cells. He thinks that water- 
vapour given off into the galleries when the stem is heated 
by the sun, would condense again on their walls and be 
reabsorbed. Further, during heavy rain, it is possible that 
a certain amount of water may find its way into the galleries, 
and probably this would be similarly absorbed by the plant. 
Thus the galleries, in addition to allowing gaseous interchange 
to take place without undue loss of water, may be perhaps, 
so far as water is concerned, an actual source of gain 3 . 
Fresh observations, if possible by direct experiment on the 
living plants, are needed to further elucidate the true function 
of the galleries. The result of one such experiment is re- 
corded by Goebel 4 . He states that a plant of P. sinuosum 
in the Buitenzorg Gardens, Java, developed side-shoots when 
its galleries were stopped with paraffin. The precise bearing 
of this on the matter in question is not quite obvious. 
1 Devaux (’99), p. 94, but cf. also (’99, 2nd paper), p. 129. 
2 Karsten, loc. cit., pp. 180 et seq. 
3 Goebel (’89), p. 208, and Forbes (’85), p. 79, record cases in which the 
galleries of certain species of Myrmecodia and Hydnophytum actually contained 
fluid water. Probably this would rarely happen in the two Polypodia, as the 
external openings are more or less ventral in position. 
4 Goebel (’88), p. 18, 
