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Show 440 UTRICULARIA MONTANA. CHAP. XVIII. <'lude that the tubers do not serve as reservoirs for food, but for water during the dry season to which the plant is probably 0xposed. The many little bladders ii lled with water ·would aid toward.s the same end. To test the correctness of this view, a small plant, growing in light peaty earth in a pot (only 4+ by 4{inches outside 1neasure) was copiously watered, and then kept without a drop of water in the hothouse. Two of the upper tubers were beforehand uncover d and measured, and then loosely covered. up again. In a fortnio·ht's time the earth in the pot appeared ex- b tre1nely dry ; but not until the thirty-fifth day were the leaves in the least affected; they then became slightly ref:lexed, though still soft and. green. This plant, which bore only ten tubers, would no doubt have resisted the drought for even a longer time, had I not previously removed three of the tubers and cut off several long rhizomes. When, on the thirty-fifth day, the earth in the pot was turned out, it appeared as dry as tho dust on a road. All the tubers had their surfaces much wrinkled, instead of being smooth and tense. They had all shrunk, but I (~annot say accurately how much ; for as they were at first syn1metricall y oval, I measured only their length and thickness ; but they con tractod in a transverse line much more in one direction than in another, so as to beco1ne greatly flattened. One of the two tubers which had been measured was now three-fourths of its original length, and two-thirds of its original thickness in the direction in which it had been measured, but in another direction only one-third of its fonner thickness. The other tuber was one-fourth shorter, one(' io·hth less thick in the direction in which it had been n1~asured, and only half as thick in another direction. A slice was cut from one of these shrivelled tubers CHAP. XVIII. UTRICULARIA NEL UMBIFOLIA. 441 and examined. The cells still contain d much wat r and no air, but they were more round d or l ss 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 a ttract1on for water ; tho shrivelled one, from which a slice had been cut, was left in water for 22 hrs. 30m., 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 kiJ?.ds 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 U tricularia are provided with these appendages ; and the group containing them has in consequence received the name of orchidioides. All the other species of U tricularia, as well as of certain clos ·1 y 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 sa1ne plant, amounting in one instance to at least twenty. UTRICULARIA NELUMBIFOLIA, AMETHYSTINA, GRIFFITHII, ClERULEA, ORBICULATA, MULTICAULIS. As I wished to ascertain whether the bladders on the rhizon1es of other species of U tricularia, and of the |