292 MODIFIED CIRCUMXUTATION. CHAI> VT 



Melilotus macrorrhiza. The plants were exposed in the same 

 manner as in the last case. Six leaves had been pinned out 

 horizontally, and five of them were killed, that is, 83 per cent. 

 We estimated that there were 200 free leaves on the plants, and 

 of these about 50 were killed and 20 badly injured, so that about 

 85 per cent, of the free leaves were killed or injured. 



Lotus aristata.Si-x. plants were exposed for nearly 5 h. to a 

 clear sky; temperature on surrounding grass 1'5 C. Four 

 leaves had been pinned out horizontally, and 2 of these suffered 

 more than those above or below on the same branches, which 

 had been allowed to go to sleep. It is rather a remarkable fact 

 that some plants of Lotus Jacobceus, an inhabitant of so hot a 

 country as the Cape Verde Islands, were exposed one night to a 

 clear sky, with the temperature of the surrounding grass - 2 C., 

 and on a second night for 30 m. with the temperature of 

 the grass between - 3 and - 4 C., and not a single leaf, either 

 the pinned-out or free ones, was in the least injured. 



Marsilea quadrifoliata. A large plant of this species the 

 only Cryptogamic plant known to sleep with some leaves pinned 

 open, was exposed for 1 h. 35 m. to a clear sky, the temperature 

 on the surrounding ground being - 2 C., and not a single leaf 

 was injured. After an interval of some days the plant was again 

 exposed for 1 h. to a clear sky, with the temperature on the 

 surrounding ground lower, viz., 4 C. Six leaves had been 

 pinned out horizontally, and all of them were utterly killed. 

 The plant had emitted long trailing stems, and these had been 

 wrapped round with a blanket, so as to protect them from the 

 frozen ground and from radiation; but a very large number 

 of leaves were left freely exposed, which had gone to sleep, 

 and of these only 12 were killed. After another interval, the 

 plant, with 9 leaves pinned out, was again exposed for 1 h., the 

 temperature on the ground being again - 4 C. Six of the leaves 

 were killed, and one which did not at first appear injured after- 

 wards became streaked with brown. The trailing branches, which 

 rested on the frozen ground, had one-half or three-quarters of their 

 leaves killed, but of the many other leaves on the plant, which 

 alone coiild be fairly compared with the pinned-out ones, none 

 appeared at; first sight to have been killed, but on careful search 

 12 were found in this state. After another interval, the plant 

 with 9 leaves pinned out, was exposed for 35-40 rn. to a cleai 

 sky and to nearly the same, or perhaps a rather lower, tempera- 

 ture Cfor the thermometer by an accident liad been left on 6 



