4 ON FLOWERS AND INSECTS. [LECT. 



the plant catches and devours the insects. 1 The first 

 observation on insect-eating flowers was made about the 

 year 1768 by our countryman Ellis. lie observed that 

 in Dionsea, a North American plant, the leaves 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 

 by a drop of an exceedingly 

 viscid solution, which, glittering 

 in the sun, has given rise to 

 the name of the plant. If any 

 object be placed on the leaf, these 

 glandular hairs slowly fold over 

 it, but if it be inorganic they 

 ,j. soon unfold again. On the other 



* hand, if any small insect alights 



FIG. 4. Drosera rotundifolia. i i 



on the leal it becomes entangled 



in the glutinous secretion, the glands close over it, 

 their secretion is increased, and they literally digest 

 their prey. Mr. Frank Darwin has recently shown 

 that plants supplied with insects grow more vigorously 

 than those not so fed. It is very curious that while 

 the glands are so sensitive that even an object weighing 

 only y^T^yth of a grain placed on them is sufficient to 

 cause motion, yet they are " insensible to the weight and 

 repeated blows of drops " of even heavy rain. 



Drosera, however, is not our only English insect- 

 1 See Darwin's Insectivorous Plants. 



