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 and 1862). 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 j, 

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

 small animals occurs in the leaves. 



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



9 Mori, A. (i 876) noted that the central region of the leaf was irritable. 



