' : \ 

 102 MOUNTAIN AND MOORLAND 



it, and to verify the fact that the news spreads to 

 neighbour tentacles which come to help. By and by, 

 as Darwin said, the Sundew leaf is like a closed fist, 

 and the insect is pinned down upon the centre of the 

 leaf. If a microscope is available it is not difficult to 

 put the leaf on a glass slide with a big drop of water 

 and to lay a cover-slip over it, so that one may see 

 something more of the wonderful hairs which have 

 been changed or evolved into tentacles. If a little 

 trace of very dilute ammonium carbonate be allowed 

 to enter under the cover-slip one has often the 

 pleasure of seeing a change travelling down the ten- 

 tacle, for the tentacles are sensitive almost beyond 

 telling to any nitrogenous substance, such as ammo- 

 nium carbonate, or the least trace of beef-tea. 



It cannot be a coincidence that there are so many 

 Butterworts and Sundews on the boggy ground. 

 This is another example of the kind of riddle that 

 rewards. These carnivorous plants grow in places, 

 such as peat bogs, where the soil has little in the way 

 of nitrogenous salts. Indeed, some of them, like the 

 Pitcher Plants, live off the ground altogether. The 

 carnivorous habit, which is like the plant turning upon 

 the animal, is an adaptation to a poor supply of the 

 absolutely essential nitrogenous food-supply abso- 

 lutely essential, as we have already mentioned, be- 

 cause all life depends chemically on the breaking down 

 and building up of proteins, which are very complex 

 nitrogenous carbon compounds. When plants can- 

 not get nitrogenous food-supplies from the soil they 

 must get them somewhere else, and one of the ways 

 is to capture insects, for their bodies contain much 

 protein material. 



