CHAP. XVIII. UTRICULARIA NELUMBIFOLIA. 441 



and examined. The cells still contained much water 

 and no air, but they were more rounded or less angular 

 than before, and their walls not nearly so straight ; it 

 was therefore clear that the cells had contracted. The 

 tubers, as long as they remain alive, have a strong 

 attraction for water ; the shrivelled one, from which a 

 slice had been cut, was left in water for 22 hrs. 30 m., 

 and its surface became as smooth and tense as it 

 originally was. On the other hand, a shrivelled tuber, 

 which by some accident had been separated from its 

 rhizome, and which appeared dead, did not swell in 

 the least, though left for several days in water. 



With many kinds of plants, tubers, bulbs, &c. no 

 doubt serve in part as reservoirs for water, but I 

 know of no case, besides the present one, of such 

 organs having been developed solely for this purpose. 

 Prof. Oliver informs me that two or three other species 

 of Utricularia are provided with these appendages ; 

 and the group containing them has in consequence 

 received the name of orchidioides. All the other 

 species of Utricularia, as well as of certain closely 

 related genera, are either aquatic or marsh plants; 

 therefore, on the principle of nearly allied plants 

 generally having a similar constitution, a never failing 

 supply of water would probably be of great importance 

 to our present species. We can thus understand the 

 meaning of the development of its tubers, and of their 

 number on the same plant, amounting in one instance 

 to at least twenty. 



UTRICULARIA NELUMBIFOLIA, AMETHYSTINA, GRIF- 

 FITHII, C^RULEA, ORBICULATA, MULTICAULIS. 



As I wished to ascertain whether the bladders on 

 the rhizomes of other species of Utricularia, and of the 



