no ALDROVANDIA [CH. 



Aldrovandia, like the Bladderworts, is able to form turions; 

 these are the size of a pea and consist of a highly abbreviated 

 axis, which may bear as many as thirty-two leaf whorls. The 

 turions normally sink to the bottom of the water in the autumn, 

 owing to the weight of starch which they contain 1 , and rise 

 again in the spring; but it seems that they sometimes fail to 

 reach the surface in the succeeding season, and that the develop- 

 ing plant may even in June be found at the bottom, held there 

 by the remains of the winter-bud 2 . When the turions are kept 

 in an aquarium indoors, it is said that they sometimes fail to 

 sink, but remain floating throughout the winter 3 . In warmer 

 climates these winter-buds are not formed; in Bengal, for in- 

 stance, the plant is described as vegetating continuously through- 

 out the year 4 . Reproduction by seed also takes place. The 

 flowers are raised above the water, but the young fruits bend 

 down, and the ripening of the seeds takes place beneath the 

 surface 5 . The structure of the embryo recalls the other Drosera- 

 ceae, the only difference being that the primary root remains 

 rudimentary. 



The leaves of Aldrovandia are highly peculiar in structure, 

 and serve, like the bladders of Utricularia^ for catching small 

 animals 6 . The broad petiole terminates in a roughly circular 

 bilobed lamina, and also bears, in its apical region, a number 

 of stiff projections, which at first glance suggest leaflets 7 , but 

 are probably only petiolar emergences 8 (Fig. 75). Long sensi- 

 tive hairs are produced from the upper surface of the lamina 

 in the neighbourhood of the midrib ; the touching of these by 

 any passing animal results in the closure of the lobes 9 , thus im- 



1 Caspary, R. (1859 anc ^ J 862). 2 Maisonneuve, D. de (1859). 



3 Schoenefeld, W. de (1860). 4 Roxburgh, W. (1832). " 



5 Caspary, R. (1859 and 1862). 



6 The proof that Aldrovandia is carnivorous is due to Cohn, F. (i 875), 

 though Delpino, F. (1871) had previously shown that the suffocation of 

 small animals occurs in the leaves. 



7 Cohn, F. (1850). 8 Caspary, R. (1859 and 1862). 



9 Mori, A. (1876) noted that the central region of the leaf was irritable. 



