4 RELA TION OF PLANTS AND INSECTS. [CHAP. 



In by far the majority of cases, the relation between 

 flowers and insects is one of mutual advantage. In 

 some plants, however, as for instance in our common 

 Drosera, we find a very different state of things, and 

 the plant catches and devours the insects.^ The first 

 observation on insect-eating flowers was made about 

 the year 1768, by our countryman Ellis. He observed 

 that in Dionaea, a North American plant, the leaves 



Fig. 4. — Drosera rotnndifoHa. 



have a joint in the middle, and thus close over, kill, 

 and actually digest any insect which may alight on 

 them. 



In our common Sundew {Drosera rotundifolia. 

 Fig. 4) the rounded leaves are covered with glutinous 

 glandular hairs or tentacles — on an average about 200 

 on a full-sized leaf. The glands are each surrounded 



' See Darwin's Insectivorous Planti. 



