PLANTS FOR THE AQUARIUM 91 



on the principle of the lobster-trap. The small organisms die 

 and decay within the traps, and the bladderwort absorbs the 

 products of decay, which serve to nourish it. The flowers are 

 yellow, and are large and handsome they are borne ~bri shoots 

 which project above the surface of the water, as in the vast 

 majority of water plants. These plants thus reproduce out 

 of the water as truly as does 

 the water-tortoise (cf. p. 99), 

 and this is one of the indica- 

 tions of a terrestrial ancestry. 

 Like Potamogeton crispus, and 

 a considerable number of 

 other water plants, Utricul- 

 aria forms special winter 

 buds. These arise at the ends 

 of the stems, and consist of 

 a great number of leaves 

 closely packed together and 

 filled with reserve food mater- 

 ial. The formation of these 

 may be noticed in the autumn, 

 when the bright green buds 

 are conspicuous among the 

 dying branches. They sink to 

 the bottom of the pond, and 

 spend the cold season in the 

 mud. With the rise of tem- 

 perature in spring they float 



Up tO the Surface and grOW FlG> ^- Po tamogeton\rispus, or curly ponct- 

 OUt into the long trailing weed. A branch taken in autumn and show- 



stems. The process can be 



perfectly well watched in an 



aquarium, and it is very interesting to collect the winter buds 



and watch the process of unfolding. Any dish of water will 



serve the purpose, and no more interesting form of simple 



aquarium can be imagined than a pie-dish containing Utricularia 



buds and tadpoles. 



Another plant which hibernates in a similar fashion by means 



in ? the be s innin s of th * .formation of a 



winter bud at the extremity. 



