86 NATURAL SCIENCE. Aug., 



for attracting or retaining insects, except, perhaps, the allure- 

 ment of a shady resting-place ; and Mr. Groom is inclined to 

 lay stress on the last point, suggesting that the existence of 

 species with merely concave leaves indicates the evolution in the 

 pitcher of an organ more perfectly adapted to provide shelter for the 

 ants on the one hand, and on the other to secure for the use of the 

 plant the materials collected by them. At the same time, he recog- 

 nises the function of storing up rain-water and the substances washed 

 down therewith. Dr. Scott and Miss Sargant also attach 

 considerable importance to the detritus in the pitchers, which is 

 proved to serve as a food-supply. They, however, find no evidence 

 of a myrmecophilous (ant-loving) habit, and agree with Treub that 

 the detritus is washed in by the rain, the pitchers serving to collect 

 rain-water, and in a less degree to economise the water of tran- 

 spiration. The upright pitchers, they remark — those, namely, with 

 the mouth at the base — "can have no other function than to store 

 up the water given ofT as vapour in transpiration. We have shown, 

 on anatomical evidence, that the inner surface of the pitcher is the 

 chief transpiring surface of the plant. The condensed water of 

 transpiration is undoubtedly re-absorbed by the roots." It is 

 difficult to follow this last observation. A pitcher turned topsy- 

 turvy could only store water in the reflexed rim, and as moisture 

 clinging round the roots, which latter would doubtless be soon 

 re- absorbed ; but why should the vapour transpired condense to 

 any appreciable amount within the pitcher ? What plays the part 

 of condenser ? Surely the economy in water of transpiration is 

 effected merely by the restriction of the area into which it is 

 transpired, which, by becoming a still atmosphere saturated with 

 water vapour, will retard further transpiration. 



The same authors give an interesting account of the purple 

 colouration on the inner surface of the pitcher, which contrasts 

 strikingly with the pale green of the outer surface. Spectroscopic 

 examination of the purple layer, also of an alcoholic extract of the 

 pigment, showed a considerable absorption of the yellow and green, 

 and almost complete absorption of the blue and violet rays. Hence 

 the green and purple layers between them cut off almost all light 

 from the interior of the pitcher, which thus forms a dark chamber, 

 into which the negatively heliotropic root is likely to be attracted. 



Fungus Parasitic on a Beetle. 



Professor Alfred Giard contributes to the Bullehn Scientifique 

 (vol. xxiv.) a study of Isaria densa, a fungus parasitic on Melolontha 

 vulgaris^ the cockchafer. He published two years ago in the Comptes 

 Rendus a notice of this fungus, and the present essay is partly an 

 amplification of it and partly a continuation of his experiences. This 

 research has been inspired with the hope of waging a successful war, 



