122 PLANTS WITH TRAPS ANIJ PITFALLS TO ENSNARE ANIMALS 



common basal cell. The basal cells themselves arc intercalateil amongst the cells 

 lining the bladder. The organic substances from the decaying bodies of captured 

 animals are sucked up by theee stellate groups of cells, and from them pass into the 

 basal cells, and later, into the other adjacent cells of the bladder and those of the 

 plant at large. 



The majority of the animals caught by the bladder.s are crustaceans. It is 

 principally larvae and adult individuals of small species of Gypri», Daphnia, and 

 Cyclops that fall into the trap; but larviB of gnats, and various other small 

 insects, little worms, and infusoria, are also not infi-equently met with imprisoned 

 in the bladders. The number of animals captured is comparatively large. In 

 single bladders the remnants of no less than twenty-four small crustaceans have 

 been observed. The prey secured by Utricularia Tninor (fig. 17), which lives in 

 little pools of still water in peat-bogs, is very abundant. The North American 

 Utricularia clandestina seems also to use its capturing apparatus with great 

 success. 



What it is that induces the animals to press upon the valves and so fall into the 

 trap is not fully explained. We may suppose that they expect to find food in the 

 bladder-cavity, or that they hope it will afford a shelter where they can rest for 

 a time and be protected from their pursuers. The last suggestion is especiallj^ 

 supported by the circumstance that the approach to the valve-covered orifice of 

 the bladder is guarded against the intrusion of larger animals by stift' sharp bristles 

 which stick out from it (fig. 18'). Only very small animals, which can easily slip 

 in between the relatively large bristles, reach the inside of the bladder, whilst 

 larger creatures, which would injure the whole apparatus, are prevented from 

 coming near it. Thus, the most probable explanation is that lesser animals pursued 

 by greater take refuge in the hiding-places behind the bristles, and so fall into the 

 trap. Another very striking fact is that the bladders of Utriculai-ise, living in still 

 water, look delusively like certain Ostracoda, especially species of the genus 

 Daphnia. The bladder itself resembles the shell-covered bodj' in size and form, 

 and the bristles the antennae and swimmerets of one of these crustaceans. Whether 

 there is any significance in this curious similarity^ of outward appearance must be 

 left undecided. 



The majority of Utriculariae live in pools of water beside foot-tracks on moors 

 and in the little collections of water between clumps of reeds in peat-bogs; and 

 these are precisely the haunts of the little creatures that are to fall into the traps. 

 Every handful of water that one scoops up contains hundreds of midge - larvte, 

 water-fleas, Ostracoda, and one-eyed Cyclops, which rush about promiscuously, 

 pursuing and seizing one another. One species of these plants lives in the moun- 

 tains of Brazil in the rain-filled receptacles of Tillavdsia plants. The Tilldndsia 

 is allied to the pine-apple, and has rosettes of concave leaves, the latter resting one 

 upon the other in such a way as to form a niche or cavity in front of each leaf 

 which fills with rain like a cistern. Many different kinds of small animals are 

 always swimming about in these little cisterns, and almost every one of the latter 



