Macaranga triloba. 
79 
MACARANGA TRILOBA : A New Myrmecophilous Plant, 
By Winifred Smith, 
University College , London. 
[With Plates V. and VI]. 
F ROM what structural feature or combination of features are 
we entitled to infer that a plant is myrmecophilous, i.e. that 
it is definitely adapted to provide attractions for ants in return for 
protection by them ? One writer considers an appropriate cavity 
for the ants to shelter in a sufficient sign of adaptation; another 
that extra-nuptial nectaries should always be present. A third 
thinks that the latter appeal no more to ants than to any other 
marauding insect with designs upon pollen, and that proteids in 
“ food-bodies ” should be offered. All look anxiously for signs of 
ants on the plants themselves and find these difficult to obtain in 
herbarium material, because the ants hurriedly leave the plants as 
soon as they are gathered, or desert them when they are drying. 
The material of Macaranga triloba on which the present observa¬ 
tions were made was collected and brought home by Mr. Tansley, 
whose attention was drawn to the apparent myrmecophily of the 
plant by Mr. H. N. Ridley, the Director of the Royal Botanic 
Gardens, Singapore. This material consists of a few dried sprays 
and three seedlings (preserved in spirit), about 12 to 18 inches high, 
which were growing wild in the Singapore gardens. The plant 
seems (so far as can be gathered from the limited material at hand) 
to unite in itself all the essential characters of myrmecophily, 
viz. an appropriate cavity as a nesting place, a thin region which 
facilitates the boring of holes for ingress, and food-bodies, conceiv¬ 
ably of a proteid nature, besides extra-nuptial nectaries—thus 
forming a combination only equalled by the two myrmecophilous 
specie^ of Acacia (A. cornigera and A. sphaerocepJiala) ( 2 ) and by 
Humboldtia laurifolia ( 1 ). The tree belongs to the tropical genus 
Macaranga of the Euphorbiaceae, and is identified as Macaranga 
triloba. The seedling has hollow internodes in the woody stems 
(see fig. 2), one peltate leaf and a pair of stipules at each node. Of 
the stipules, some are caducous, some persist. When they are 
protecting the bud, they are erect; older ones are retroverted and 
become closely appressed to the stem (see fig. 1.) 
The appropriate cavity is found in the hollow internodes, 
which are swollen in young stems. The pith seems to break down 
