NUTRITION 



3*7 



tive translucent spots away from the concealed opening, one or all, which 

 prevent the escape of insects that wander in and sooner or later drown 

 in the fluid; whence nitrogenous compounds derived from their bodies 

 by decay or digestion enter the 

 tissues of the pitcher. 



Flytrap. — Venus's flytrap 

 (Dionaea, fig. 657) has leaves 

 with two terminal lobes about 

 1 cm. long, hinged about the 

 midrib, and fringed with long 

 slender teeth, which interlock 

 when the lobes shut together (figs. 

 658, 659) , On the surface of each 

 lobe are three large sensitive bris- 

 tles, and if one of these be bent so 

 as to compress the basal cell, the 

 lobes shut like the two jaws of a 

 trap. Insects, flying or crawling, 

 which come into contact with the 

 bristles are often caught. Then 

 the glands upon the upper (in- 

 ner) surface pour out a digestive 

 fluid, the proteins are reduced 

 to such simplicity that they can 

 enter the tissues, and after a few 

 days the leaf opens again. Its 

 water mate, Aldrovanda, has a 

 similar but smaller trap, by which 

 minute swimming crustaceans, 

 Daphnia, Cyclops, etc., are often 

 caught. 



Sundew. — Droscra, the sun- 

 dew, has its leaves (fig. 685) 



Figs. 658, 659. — Cross sections of the termi- 

 nal lobes forming the "trap" of Dionaea: 

 658, enlarged view, closed position, diagram- 

 matic; g, digestive glands;/?, ^.parenchymatous 

 tissues whose varying turgor opens and closes 

 the "trap"; s, sensitive bristles; 659, outline, 

 fringed and covered above with on a smaller scale, of same in an open position. 



stalked glands that secrete a ~~ After Kny - 



viscid transparent fluid, in which small insects alighting may become 

 enveloped by their own struggles, and further (in our species) on account 

 of the inflection of the stalks of the glands. When an insect is caught, 

 the character of the secretion changes; it becomes more watery and 



