Ridley.—Symbiosis of Ants and Plants. 465 
I moved some plants from the Durian tree to a shady tree near 
my house, and they were invaded by a species of ant, apparently the 
same one which frequents the roots of epiphytic orchids. They piled up 
earth on the basal ends of the deflexed pitchers among the roots of the 
Dischidia , and on opening one of the pitchers I found that it contained 
numerous workers, with a queen and a number of eggs, some of which 
had hatched out. There was no soil or other material in the pitcher. 
I conclude from these observations that Dischidia Rafflesiana cannot 
be considered as truly myrmecophilous. 
Polypodium sinuosum. 
The morphology of this plant is described by Yapp in Annals of 
Botany, vol. xvi, p. 185, Pis. X, XI, XII. The plant is common in 
Singapore. It is an epiphytic fern with a thick rhizome, tunnelled for 
almost its whole length and inhabited by the ant Technomyrmex albipes , Sm., 
of which Bingham says, in the Formicidae of the Fauna of British India, 
‘ Occurs throughout our limits and spread over the tropics of the old world.’ 
This species is frequently imported into Europe with tropical plants; 
I have seen many specimens from Kew Gardens, so that it does not appear 
to be peculiar to the Polypodmm, which has not so wide a distribution. As 
Yapp explains, a tissue consisting of large cells with thin walls and no 
intercellular spaces is formed in certain definite areas near the apex of the 
stem ; this tissue breaks down at an early period, its place being taken by 
ant galleries. The communication with the outer air is effected by short 
passages excavated by the ants themselves. 
The position of this tissue seems, he says, to indicate that this was 
developed originally as a water reservoir, but as it soon disappears it may 
perhaps have to some degree changed its function, and the galleries may 
have some other important function to fulfil. He suggests that they may 
serve as organs for the aeration of the stem, and to a slight extent for the 
absorption of water. 
The fern generally grows in at least partially shaded though not 
heavily shaded spots, on the boughs of trees, at about 15 to 20 feet from the 
ground. Like the other myrmecophilous fern described in the same paper, 
Lecanopteris carnosa , a nearly allied plant, it seems almost impossible 
to cultivate it away from its ordinary habitat; even if a bough carrying it is 
carefully cut off and transferred to a shady spot, it very speedily perishes, 
so much so that the native gardeners affirmed it would never grow but 
on a living tree. 
No epiphytic fern native here appears to suffer so much from drought. 
A few weeks of dry weather on one occasion in the Gardens almost 
exterminated the plant altogether, though it was very abundant on the 
branches of a shady Inga saman , as well as elsewhere in the Gardens. 
H h 
