140 LIFE OF 



the model, to depart from which will but sow hindrances 

 in the path of scientific progress. 



The order to which the butterwort and the bladderworts 

 belong also afforded valuable results. The leaf of the 

 butterwort bears glandular hairs, and its margins curve 

 inwards when excited by contact of various bodies, 

 especially living insects, and, at the same time, these are 

 caught in the viscid secretion of the glands, and their 

 juices absorbed by the plant. The bladderworts are 

 even more remarkably constructed, for they have a 

 portion of their leaves developed into subaqueous 

 bladders, with a narrow entrance beneath, defended by 

 a complex valve, which facilitates the entrance of water 

 insects or crustaceans, but prevents their exit. The whole 

 interior of the bladder is lined with transparent four- 

 branched protoplasmic hairs, but nevertheless the bladder- 

 wort is unlike the preceding plants in having no power of 

 digesting its prey, however long it may remain in cap- 

 tivity. Yet there is no doubt that the imprisoned 

 creatures do decay in their watery cell, and that the hairs 

 just described absorb the products of their decay. 



Such is a brief account of Darwin's work on " Insec- 

 tivorous Plants." With his characteristic expressions he 

 acknowledges the valuable aid given him by Professor 

 Burdon-Sanderson, and by his son, Mr. Francis Darwin. 

 The former was enabled to give the first brief account of 

 the process of digestion in these plants, as observed by 

 Darwin, in a lecture before the Royal Institution, in 

 June, 1874, and Dr. (now Sir Joseph) Hooker called 

 general public notice to the subject of Carnivorous 

 Plants in his lecture before the British Association at 



