62 



S YMBIOSIS—DISJ UNCTI VE 



opens again. The whole process from the capture of the insect to 

 the opening of the trap may take several days but there are some- 

 times victims in several traps of one plant at the same time. 



The bladderworts (Utricularia) belong to the same family as the 

 butterworts but they are quite different appearing plants. There 

 are a considerable number of species, most of which grow in the 

 water of ponds, swamps or bogs. Most of them are free-floating 

 but a few are rooted in the mud along the edges of ponds. The 

 floating forms are often entirely without roots but have very much 

 dissected submersed leaves which serve as absorbing organs. On 

 these submersed leaves are found numerous small bladders each 







Fig. 23.— Venus's flytrap. (Photograph by B. W. Wells.) 



with an opening at one end which is furnished with a valve-like lid 

 and usually a few stiff bristles pointing inward, much like the 

 entrance to an eel trap. ^Yhen the trap is "set" for a catch the sides 

 of the walls of the bladder are compressed. Any small animal that 

 chances to swim into the vestibule may come in contact with the 

 bristles and cause tlie walls of the bladder to expand and the valve 

 to open. Then water is sucked into the bladder with a rush and any 

 small animals in the vicinity are carried in witli it. The trap is then 

 slowly set for another catch, the entire process taking about twenty 

 minutes. There is considerable evidence that the animals thus 

 captured are digested and absorbed by the plant. It is believed 

 that a single plant, under favorable conditions, may capture several 

 thousands of minute animals in a single day. 



