268 ABSOBPTION OF NUTRIMENT BY INSECTIVOKOUS PLANTS. 



01^ THE ABSORPTION OF NUTRIENT MATERIAL BY THE 



LEAVES OF SOME INSECTIVOROUS PLANTS. 



By J. W. Clabk. 



In a report* of Dr. Balfour's interesting and important experi- 

 ments recently read before the Botanical Society of Edinburgh, occurs 

 the following passage in reference to the absorption of insects and 

 other nutrient material by the leaves of the Bioncea Muscipula. 

 " The notion that any nourishment was obtained from insects so en- 

 closed has been controverted ; but Dr. Balfour pointed significantly to 

 the fact that young plants of Bmicea under bell-glasses had not been 

 found to thrive so well as those left free, and that while a piece of beef 

 in another leaf became putrid, a piece enclosed by the Dioncea re- 

 mained perfectly fresh and inodorous, but soon lost its red colour, 

 and was gradually disintegrated more and more until it was reduced 

 to pulp." Thus not only does the proof of absorption by the leaves 

 of insectivorous plants rest upon indirect or unsatisfactory evidence,! 

 but considerable diversity of opinion appears to exist upon the subject, 

 and it was in hopes that some conclusive proof might be obtained and 

 all doubt removed that the following experiments were made. 



Series I. — Drosera rotundifoliaX and D. intermedia. 



Locality. — An unlimited supply of these plants could be obtained 

 from some marsh land in the New Forest, a few miles from South- 

 ampton, where the following experiments were carried on. 



Method of preparation. — In these experiments the delicacy and 

 certainty of the spectroscopic test for lithium was made use of,§ and 

 the lithium applied to the plants by means of flies, which, after their 

 wings and legs had been removed, were macerated in a strong solution 

 of citrate of lithium, cut up into suitable sized pieces and placed 

 upon those leaves which had been selected and prepared to receive 

 them. 



By placing the plants in the pots rather higher than the surround- 

 ing earth, the leaf-stalks could easily be brought into a horizontal 

 position or caused to bend downwards towards the blade of the leaf, 

 at a considerable angle from the plant, thus lessening the possibility of 

 the lithium getting on the leaf-stalk : when necessary the leaves were 

 retained in this position by peculiarly shaped pins. 



When the plants had been thus potted and supplied with prepared 

 flies, they were one by one put into a zinc tank about two inches 

 deep, with half an inch of water on the bottom, and enclosed by a fine 

 gauze cage, thus preventing insects getting in and carrying the 

 lithium on to other parts of the plant. For further protection this 

 was kept in an open greenhouse where the temperature was but little 

 above that of the air outside. 



♦ " Pharmaceutical Journal," July 3, 1875. 



t The above was written before I was aware of the publication of Mr. 

 Darwin's work on Insectivorous Plants. 



X D. rotundifolia has been mostly employed in these experiments on ac- 

 count of its Ijirger and more conveniently shaped leaves. 



§ Other methods have been tried, but this has proved the most succesBful. 



