106 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



air-bladders, slowly rises, and comes to float at the surface. 

 Flowering takes place in the air ; when it is over, the root 

 recommences to secrete mucus which replaces the air in the 

 bladders, so that the plant becomes heavier and sinks to the 

 bottom, where it ripens its seed at the spot where they are to be 

 sown." 



Such a view is obviously incorrect for various reasons. In 

 the first place it does not take into account the occurrence of 

 bladders on the land-forms of Utricularia. Moreover the blad- 

 ders of floating plants are by no means always filled with air ; 

 and Darwin has shown (" Insectivorous Plants," 1875, p. 404), 

 that plants from which the bladders have been removed still 

 continue to float. On the other hand, the observations of 

 Darwin (loc. cit.), Cohn ("Beitr. zur Biol. d. Pflanzen," I., 

 1875), and others (see Goebel, " Pflanzenbiologische Schilder- 

 ungen," II.), establish beyond doubt that these bladders are 

 traps ; when the animals have once entered, escape is rendered 

 impossible by the closing of the valve guarding the orifice. 



Since the plant produces such an elaborate mechanism for 

 the capture of animals, the inference is obvious that some benefit 

 must be gained thereby for the plant ; the observations of Biisgen 

 (" Ber. deut. bot. Ges.," 1888) prove, in fact, that plants thus 

 supplied with animal food grow more vigorously than similar 

 plants without it. The captured animals undergo disintegra- 

 tion in the bladders, and the organic products of the disintegra- 

 tion are absorbed by the plant, the process of absorption being 

 effected by the quadrifid or bifid hairs which are scattered over 

 the internal surface of the bladder. But it has not been ascer- 

 tained whether the disintegration of the captured animals is 

 effected by an enzyme secreted by the bladder, or is the result 

 of putrefaction induced by Bacteria. 



The pitchers of Genlisea, though they are adapted to catch 

 subterranean animals, are altogether different in their form and 

 mechanism from the bladders of Utricularia with which genus 

 (icnlisea is closely allied. The pitcher has somewhat the 

 shape of a thermometer : the narrow orifice is continued, as it 

 were, at each side into a canal formed by the long spirally 

 wound appendages to which attention has been already drawn, 

 and which penetrate into the soil. The orifice opens into a 

 long narrow tubular neck the inner surface is covered by stiff 



