CLIMBERS, PARASITES, SAPROPHYTES. 209 



the flowering shoots project above the water. The submerged 

 parts bear curious bladders, each with a trap-door or valve 

 which is easily opened by a push from the outside, so that 

 small animals (insects, water-mites, water-fleas, etc.) cannot 

 escape once they have entered the bladder. When these 

 animals die their soft parts decay and are absorbed by 

 branched hairs which occur on the inner surface of the 

 bladder. 



The leaves of Venus' Fly-trap 1 are two-lobed, and the 

 midrib acts as a hinge. Each lobe bears on its upper surface 

 three long sensitive hairs, and when one of these hairs is 

 touched, the two lobes snap together, just as one closes an 

 open book, and capture the insect that has caused the dis- 

 turbance (Fig. 66). Digestion occurs as in Sundew. The 

 leaves of Venus' Fly-trap are only slightly sensitive to 

 chemical stimuli, but if the closing of the lobes has been 



SENSITIVE SK, > 7?. MIDRIB 

 HAIRS 



Fig. 66. Venus' Fly-Trap (Dionaea nmacipnlaX 



caused by an insect they press tightly against each other and 

 hold the insect fast (the interlocking teeth on the edges of 

 the lobes prevent its escape after the sensitive hairs have 

 been stimulated), whereas the closing remains incomplete, 

 leaving a wide space between the lobes, if the hairs have 

 been touched by, say, a pencil. In the latter case the leaf 

 opens again, but if an insect has been caught the leaf remains 

 closed until the digested products Lave been absorbed. 



1 A native of Carolina, where it grows in SM'amps ; often cultivated 

 in hot -houses. 



S. B. 14 



