94 UTRICULARIA [CH. 



showed that in herbarium specimens of Utricularia vulgaris the 

 bladders often contained skeletal tissues of Crustacea and insect 

 larvae. He then tried the experiment of putting a living shoot 

 of this plant, which had empty utricles, into water rich in Cypris\ 

 next morning nearly all the bladders contained Crustacea, 

 swimming about in a restless manner but unable to escape. 

 Rotifers, Infusoria, Rhizopods and other animals were also 

 present ; certain bladders containing as many as six living Crus- 

 tacea, as well as other animals, were described by the observer 

 as " a little menagerie of the microscopic water fauna." The 

 number of animals secured may sometimes be very great. It 

 has been recorded, for instance, that a plant of the Common 

 Bladderwort, introduced into water rich in Daphnidae, in one 

 case was found after 1 1 hours to have caught as many as twelve 

 of these little Crustacea in a single bladder 1 . Another plant, 

 which was about 1 5 cms. long, and bore fifteen fully developed 

 leaves, each with about six bladders, is reckoned to have en- 

 trapped at one time as many as 270 individuals of Chydorus 

 sphaericus 1 . It is a curious fact that different species of Utricu- 

 laria^ even when growing associated in the same water, may, 

 owing to some slight difference of habit, catch quite different 

 animals. In one case Goebel 2 observed U. intermedia and U. 

 vulgaris growing together, but while U. intermedia had caught 

 chiefly Cypris, U. vulgaris had caught only Copepods. This is 

 to be explained by the fact that U. intermedia^ being anchored 

 at the bottom of the water, was only able to secure the Cypris, 

 which is a creeping form, while the Copepods, because they 

 were free-swimming, were entrapped by the bladders of the 

 unattached U. vulgaris. The animals are said to be attracted by 

 edible mucilage secreted by the hairs which grow on the blad- 

 ders of the Utricularias (Fig. 62), and especially on the valve 

 at the aperture 2 . 



The observations which we have enumerated and many 

 others which might be cited, leave no room for doubt that the 



iBusgen, M. (1888). 



2 Goebel, K. (1891-1893). 



