Chap IV. 



DICOTYLEDONS. 



227 



served, and some of them with the greatest care, the 

 periodical movemeuts of leaves ; bat their attention 

 has been chiefly, though not exclusively, directed to 

 those which move largely and are commonly said to 

 sleep at night. From considerations hereafter to be 

 given, plants of this nature are here excluded, and 

 will bo treated of separately. As we wished to ascer- 

 tain whether all young and growing leaves circumnu- 

 tated, we thought that it would be sufficient if we 

 observed between 30 and 40 genera, widely distributed 

 throughout the vegetable series, selecting some un- 

 usual forms and others on woody plants. All the 

 plants were healthy and grew in pots. They were 

 illuminated from above, but the light perhaps was not 

 always sufficiently bright, as many of them were ob- 

 served under a skylight of ground-glass. Except in a 

 few specified cases, a fine glass filament with two minute 

 triangles of paper was fixed to the leaves, and their 

 movements were traced on a 

 , vertical glass (when not stated 

 to the contrary) in the manner 

 already described. I may repeat 

 that the broken lines represent 

 the nocturnal course. The stem 

 was always secured to a stick, 

 close to the base of the leaf 

 under observation. The ar- 

 rangement of the species, with 

 the number of the Family ap- 

 pended, is the same as in the 

 case of stems. 



Fig. 93. 



Sarrocenia purpurea : circum- 

 nutation of young pitcher, 

 traced from 8 A.M. July .Srd 

 to 10.15 A.M. 4th. Temp. 

 17°-] 8° C. Apex of pitcher 

 20 inches from glass, so 

 movement greatly mag- 

 nified. 



(1.) Sarracenia purpurea (Sarra- 

 cenese, Fam. 11).— A young leaf, or 



pitcher, 8^ inches in height, with the bladder swollen, but with 

 the hood not as yet open, had a filament fixed transversely 



