VIIl] 



CARNIVOROUS HABIT 



III 



prisoning the prey. The sensitiveness of the leaves is greatest 

 at rather high temperatures^. The Linnean name, '^ vesiculosa^'' 

 is an unfortunate one, since it suggests that the leaves form 

 actual bladders, whereas the lobes merely fold together like 

 those ol Dionaea. Besides the irritable hairs, glands^ are also 

 present, which apparently secrete a digestive fluid and absorb 

 organic matter^. 



There is good reason to suppose that both Aldrovandia and 

 the water Utricularias are descended from terrestrial ancestors 



Fig. 75. Aldrovandia vesiculosa, L. i, whorl of leaves (about ^ nat. size); 2 and 3, 

 individual leaves (x 2 J circa). Leaf is shown in natural position in 2, and with the 

 lobes open in 3. [Adapted from Caspary, R. (1859).] 



which were already carnivorous. Aldrovandia is the only 

 aquatic member of the Droseraceae, a family which contains 

 well-known insectivorous types such as the Sundew, while the 

 aquatic Utricularias are associated both with terrestrial car- 

 nivorous members of the same genus, and with the insect- 

 catching Pinguiculas, which are not hydrophytes. The habit of 

 consuming animal food has thus not arisen de novo in connexion 

 with an aquatic existence, though this mode of life undoubtedly 

 affords unique opportunities to a carnivorous plant*. 



^ Stein, B. (1874). 2 Fenner, C. A. (1904). 



3 Darwin, C. (1875). 



* On Aldrovandia^ in addition to the papers cited in this chapter, see 

 Caspary, R. (1858^) and Hausleutner (1850^) and (1851). 



