1912] CURRENT LITERATURE 83 
Symbiosis of ants and plants.—Rup.ey,®* as director of the botanic gardens 
at Singapore, has had exceptionally good opportunities to examine the so- 
called “‘myrmecophilous plants” of the eastern tropics, and he has reported his 
studies of more than a dozen such cases of symbiosis. His observations appear 
to have been carefully made and accurately recorded, and must be regarded as 
a considerable contribution to our knowledge of the relationship existing 
- between these two organisms, even if we do not agree with all his interpretations 
of the facts. 
A very considerable number of such plants afford a convenient sheltering 
home for the ants, either within hollow organs, such as thorns or stems, or 
within the leaves or flowers. The ants, however, obtain no food from the 
plant, nor do they benefit it in any way. Examples of this class are Dischidia 
Rafflesiana and several species of rattan. In Goniothalmus Ridleyi it seems 
likely that the ants effect pollination while nesting in and about its flowers. 
In the second class of myrmecophilous plants, there seems to be a relation- 
ship which is mutually advantageous between many epiphytic ferns and 
orchids, whose roots afford an excellent shelter, and the insects that, in con- 
structing their nests, bring up considerable quantities of soil and heap it about 
the base of the plants. To this class belong Thamnopteris nidus-avis, Platy- 
certum biforme, and a considerable number of orchids. 
A third class consists of two small trees, Macaranga triloba and M. Griffthi- 
ana, whose hollow stems are pierced and tenanted by ants. In both species 
the stipules are persistent and possess glands which secrete waxy granules 
that the ants gather and use as food. In return for this shelter and food, 
Riptey declares that the ants protect the trees from the attacks of caterpillars, 
although his only evidence seems to be that the trees tenanted by ants were 
not damaged by caterpillars, while certain others had their leaves somewhat 
eaten. He concludes that “the hollow stem, the retention of the stipules 
for some time after their original function of protecting the bud has ceased 
to be necessary, and the production of food bodies, are all modifications which 
can have no other function than that of attracting the ants and retaining their 
services as guards.”—Gro. D. FULLER. 
Movement of water in plants.—In a brilliant and ingenious piece of work 
on the movement of water in plants, RENNER™ has brought some telling evi- 
dence for Drxon’s cohesion theory of the rise of sap. The evidence, too, is 
worked out by the use of that rather discredited instrument, the potometer. 
The cohesion theory, unlike the other conceptions of the rise of sap, has sound 
physics to recommend it, and now RENNER is able to measure suction in trans- 
piring twigs amounting to 10-20 atmospheres, a thing that the cohesion theory 
assumes to exist. The “saturation deficit” is conceded by RENNER as the 
*3 RipLey, H. M., Symbiosis of ants and plants. Ann. Botany 24:457-483. rgro. 
™4 RENNER, O., omega Beitrage zur Kenntnis der Wasserbewegung. 
Flora 103: ise-gas. gir 
