24 



M0VE3IENTS OF LEAVES. 



tlio clow is oil, Avhilo othei\s rarely evor open at all, but remain 

 closed. 



Tlio leaves of Leersiu (riee eut-grass) are most instructive with 

 their bulljform cells above unci below. These penetrate tlie bliule 

 deeply and luake it very sensitive. In a warm day a brisk rub, 

 or more than one between thumb and finger, causes it to close in a 

 few seconds. After a sliort interval tlie leaf oi)ens again, when it 

 will be ready io respond to the same experiment. 



Tlie leaves of Paninnn jilicatiiin, when dry, close in a zigzag 

 manner like a fan. 



The bulliform cells of the leaves of Phlenm j)i'ateHse (Timothy) 

 and Alopectinis j)r(ifciisis (meadow foxtail) are not very large, 

 and do not penetrate deeply. Such leaves are not good ' * rollers. '' 



In case of leaves like Sj)oi'oboIi(s and others, the bulliform 

 cells are large, the groups numerous, and penetrate di'cply. 

 These leaves arc likely to remain rolled up for a good portion of 

 the time, unless the weather is verv moist. 



Fi<!. ;i7. -TransvtM'Sfsei'tion of iisninU 

 jjortioii of a Made of S)>()r<ihi)Ui!< ('r//|)- 

 tniuir^its showiiiii bullifdnii ci'Us, iii 

 wliich tliorc IS a niiigU' larne one, 

 deeply penetratiiii; and some smaller 

 I'ells at the side. 1 x 17'>.— (Sudworth.) 



Fro. .TS.— Section of a leaf-blade 

 of Hicriwhhxi ctliHiui. 1x^4. 

 (Sudworth.) 



Fio. .TO.— Seotionof a leaf-blade of Stipa '•partea well adapted for closinji in dry 

 weadier. 1 x Ul.-(Sudworth.) 



