296 Scientific Proceedings, Royal l)ublin Society. 



number of stomata on the upper and lower surface is practically the same ; 

 but in the shade form they are about four times more numerous on the lower 

 surface. In both forms water-pores occur on the upper surface. 



Relations with Ants. 



Both of the species of Dischidia under consideration harbour ants. They 

 are not unique in this respect, as ants have been noticed in connexion with 

 several other species of tiiis genus. 



In D. nummularia the ants are found beneath the leaves, where they form 

 nests of clay and vegetable debris, in wliicli the roots of the Dischidia branch 

 freely. The ants also make passages, covered in with the same material as 

 that of the nest, wliich run in the crevices of .the bark down the trunk to the 

 ground, and along many of the branches to their leafy extremities. 



I was able, tlirough the kind offices of the autliorities of the Britisli 

 Museum, to obtain identification of these and other ants from Dr. Forel. 

 They proved to belong to two species of Iridomyrmex — /. myrmecodice, Emeiy, 

 and a new variety, Waldoi, Forel, of /. coidatus, Smith. Sometimes a small 

 black ant, Cataulacus (jranulntus, Latr., sub-sp. hisjndiis. Smith, was found 

 wandering about plants of D. numiimlaria, but always in small numbers, and 

 apparently in perfect agreement with Iridomyrmex. 



In May, June, and July of 1911, I examined eighty-one plants of 

 D. mimmularia growing naturally, taking them consecutively, except that I 

 only counted one plant on each tree, and did not count any plant which was 

 on the same tree as D. raffiesiana. Iridomyrmex was found nesting under the 

 leaves of seventy-seven of the eighty-one plants examined. In three of the 

 four plants where Iridomyrmex was not found their deserted nests were 

 present under the leaves, and their runs on the trunk of the host-tree. In 

 two of these three cases other ants were present in large numbers on the 

 tree — Dolichodevus bituberculatus, Mayr, in one, (Ecophylla sniaragdina, Fabr., 

 in the other. They had possibly driven away the Iridomyrmex. The fourth 

 plant was in a dying condition ; there were termite runs about the tree and 

 under the dying plant. 



Of the eighty-oue plants examined, therefore, eighty either had a species 

 of Iridomyrmex actually living under tlieir leaves, or there was evidence of its 

 recent presence, the only plant with no sign of Iridomyrmex being in a dying 

 condition. I think, then, we may conclude that, as far as Northern Siam is 

 concerned, Dischidia nummularia normally harbours one of the above species 

 of Iridomyrmex. These two species of Iridomyrmex appear very similar to 

 one wlio is not an entomologist ; and it was not until I had sent to London 



