CHAP. VI. USE OF SLEEP MOVEMENTS. 291 



killed, and none of the many free leaves on the several plants 

 were at all injured, with the doubtful exception of two or 

 three very young ones. 



Melilotus Jtalica. Six leaves were pinned out horizontally, 

 three with their upper and three with their lower surfaces turned 

 to the zenith. The plants were exposed for 5 h. to a clear sky, 

 the temperature on ground being about - 1 C. Next morning 

 the six pinned-open leaves seemed more injured even than the 

 younger and more tender free ones on the same branches. The 

 exposure, however, had been too long, for after an interval of 

 some days many of the free leaves seemed in almost as bad a 

 condition as the pinned-out ones. It was not possible to decide 

 whether the leaves with their upper or those with their lower 

 surfaces turned to the zenith had suffered most. 



Melilotus suavtolet/s. Some plants with 8 leaves pinned out 

 were exposed to a clear sky during 2 h., the temperature on the 

 surrounding grass being - 2 C. Next morning 6 out of these 

 8 leaves were in a flaccid condition. There were about 150 free 

 leaves on the plant, and none of these were injured, except 2 or 3 

 very young ones. But after two days, the plants having been 

 brought back into the greenhouse, the 6 pinned-out leaves all 

 recovered. 



Melilotw Taurica. Several plants were exposed for 5 h, during 

 two nights to a clear sky and slight frost, accompanied by some 

 wind ; and 5 leaves which had been pinned out suffered more 

 than those both above and below on the same branches which 

 had gone to sleep. Another pot, which had likewise been kept 

 in the greenhouse, was exposed for 35-40 m. to a clear sky, 

 the-temperature of the surrounding grass being between - 3 and 

 - 4 C. Nine leaves had been pinned out, and all of these were 

 killed. On the same plants there were 210 free leaves, which 

 had been allowed to go to sleep, and of these about 80 were 

 killed, i.e. only 38 per cent. 



Melilotus Petitpitrrtana. The plants were exposed to a clear 

 sky for 35^0 m. : temperature on surrounding grass 3 to 

 4 C. Six leaves had been pinned out so as to stand about 

 i inch above the cork, and four had been pinned close to it. 

 These 10 leaves were all killed, but the closely pinned ones 

 suffered most, as 4 of the 6 which stood above the cork still 

 retained small patches of a green colour. A considerable 

 number, but not nearly all, of the free leaves, were killed or 

 much injured, whereas all the pinned out ones were killed. 



