Onar. XVIII. UTRICULARIA NELUMBIFOLIA, 44] 
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, CARULEA, ORBICULATA, MULTICAULIS. 
As I wished to ascertain whether the bladders on 
the rhizomes of other species of Utricularia, and of the 
