44O CHARACTER OF VEGETABLE VITALITY. CHAP. XI. 



SUBSECTION I. 



Action of Light. The stimulating influence of 

 light upon the vital principle of the plant is dis- 

 coverable, whether in the stem, leaf, or flower. 

 The direction of the stem is influenced by the 

 action of light. 



Jnfluenc- If a plant is placed in a room or cave in which 

 rection of" there is only one small aperture for the admission 

 ttoiten, Q f ijgj^ the gtem w iH g ra d ua liy bend towards that 



aperture. Bonnet sowed some French Beans in a 

 dark cave, with a view to ascertain the effect of the 

 small portion of light transmitted to them through 

 the entrance : the stem was a little inclined to- 

 wards the entrance during the day, but it re- 

 gained its erect position partially at least during 

 the night. 



The vl- The vigour and colour of the stem are also af- 

 cobur"of fected by the presence or absence of light. If a 

 the plant, cu ^ting of Potatoe is left to vegetate in a cellar, 

 where there is but little access to light and air, the 

 stem will shoot out to a great length in the direc- 

 tion of the light ; but pale, and limber, and trailing 

 on the floor, Bonnet planted three Beans for the 

 purpose of comparative experiment, one in the 

 open air, another in a tube of glass covered at the 

 top ; and a third in a tube of wood covered at the 

 top also. The first plant was strong and luxuriant ; 

 the second was also strong, and inclined towards the 



