202 



BRITISH FLOWERING PLANTS 



recently been studied by an American botanist, Mr. 

 Canby, who found, by feeding the leaves with small 

 pieces of beef, that these were completely dissolved and 

 absorbed ; the leaf opening again with a dry surface, 

 and ready for another meal, though with an appetite 

 somewhat jaded. Cheese disagreed with the leaves, 

 turning them black, and finally killing them. 



In the case of Drosera the leaves are covered with 

 gland-bearing filaments or tentacles. Each gland is 



surrounded by a drop of viscid 

 secretion, which, glittering in 

 the sunshine, have given the 

 plant its poetical name of Sun- 

 dew. There are about 200 on 

 each leaf If a small insect — 

 and the victims are mostly small 

 flies — alight on the leaf, it is 

 caught by the viscid secretion. 

 The gland is immediately excited 

 to more active secretion, and the 

 stimulus gradually extends to 

 the whole leaf The tentacles 

 also bend over towards the in- 

 sect, which is firmly held (Fig. 

 140). The secretion becomes 

 more viscid, and the softer parts 

 of the captive are dissolved and 

 digested. When all the nourishment has been ex- 

 tracted, the secretion dries up, the tentacles resume 

 their original position, the hard parts of the insect 

 are blown away, and the leaf is ready for another 

 meal. On one large leaf Darwin found the remains of 

 no less than thirteen insects. Mr. Francis Darwin has 

 found that plants fed on small bits of meat were more 

 vigorous than others which were kept without animal 

 food and left to depend on their roots alone. 



The sensitiveness of the tentacles is marvellous. 

 Darwin found that a minute particle of a woman's hair 

 weighing ysy^j^ of a grain produced a distinct move- 



FlG. 139. — Drosera anglica. 

 Plant (reduced) with pistil 

 and seed. 



