II Pitcher Plmits 33 



stances would have formed the stomata of an aerial leaf 

 (See Chap. IX.) 



The seasonal life of the aquatic bladderwort is interest- 

 ing. Throughout the summer it floats on the surface of 

 the water, and the straggling stem grows at one end as it 

 dies away at the other. Perhaps too many decomposing 

 Crustaceans, however good for the growth of the plant, 

 may not be altogether good for the leaves which most 

 directly receive this liberal manuring. As the summer 

 ends, and as the water-fleas cease to swarm in the pond, 

 the life of the plant becomes concentrated in a thick-set 

 terminal tuft. This, as in some other aquatic plants, sinks 

 to the bottom of the pond and passes the winter there. 

 In spring, lightened perhaps of what stores of reserve 

 material it contained, the stem rises again, and forming a 

 fresh set of bladders begins to grow vigorously at the 

 surface. The older botanists, e.g. A. P. de Candolle, 

 believed that the bladders were floats for the plants ; at 

 first they were filled with mucus, and the plant rested at 

 the bottom ; afterwards they were filled with gas, and the 

 plant rose to the surface. This was a pretty notion, but not 

 true. The plant will float without any bladders, or when 

 all are full of water ; the bladders have really nothing to do 

 with the floating. 



Bionomics of Bladderwort. — It may be that the water- 

 fleas enter the bladders in search of Infusorians and other 

 small creatures on which they feed ; it seems likely, too, 

 that the bladderwort does really profit by the capture of 

 the water- fleas. There is another strand in the web. 

 Amid the Utricularia one commonly finds certain water- 

 spiders, who make for themselves a diving-bell with air 

 which they carry from the surface, their bubble glistening 

 like silver as they descend. Have not these clever crea- 

 tures come to recognise that the bladders of Utricularia 



D 



