SOME PLANTS WHICH I-:. MUM' INSECTS. 417 



SOME PLANTS WHICH ENTKAP [NSECTS. 



By FORREST SHREVK, 



THE JOHNS HOPKINS UNIVERSITY. 



WE seldom give a thought to the fact that plants need food. 

 They had such unite, motionless lives that it is difficult to 

 believe that they have, like ourselves, a bread-and-butter problem 

 staring them constantly in the face. We watch the geraniums and 

 begonias of our window-garden grow and hloom with nothing to 

 nourish them but a few handfuls of earth and a little water. Surely 

 their food problem must be a simple one if the suhstances necessary to 

 the formation of stem and leaves and blossom can all be got from so 

 little earth. Wherein lies all the difficulty about poor soil which besets 

 the farmer, and why must he buy tons of plant food and drill it care- 

 fully into the ground in order to get a remunerative crop of grain? 

 The whole trouble for the farmer arises from the scarcity in the soil 

 of two or three food elements which, although highly important, form 

 I tut a small part of the total weight of growing plants. The foremost 

 of these scarcer foods, nitrogen, has been a source of difficulty not only 

 to man, but to a large number of plants as well, which have been forced 

 to adopt a means of getting it which is radically different from all 

 other methods of plant nutrition, so much so indeed that it was long 

 looked upon as a mere meaningless 'freak of nature.' This method 

 is the catching of insects. 



Every one has heard of the pitcher-plant or perhaps seen its urn- 

 like leaves half filled with water. Innocent looking as are these leaf- 

 pitchers, and casual as may seem the presence of three or four drowned 

 flies in the water which they contain, yet in truth each pitcher is a 

 veritable trap, clever in design and effective in its purpose of alluring 

 and drowning insects. Different in look, but to the same purpose, are 

 the leaves of the sun-dew. Its bristling hairs bear beads of jelly, not 

 for the mere splendor of their dazzling brilliance, but to allure, catch 

 and hold fast gnats and mosquitoes, all to the same end as in the 

 pitcher-plant, — supplying a shortage of nitrogen in the food. Not 

 these two plants alone, but a large group of nearly four hundred 

 species, are insect trappers, carnivorous or, as they are more commonly 

 called, insectivorous plants. The varied devices which these plants 

 possess for alluring insect prey, catching, holding and utilizing it 

 furnish matter for one of the most interesting chapters in all botanical 

 science. 



VOL. LXV. — 27. 



