16 



BEHAVIOR OF STOMATA. 



with plants grown in a greenhouse under shaded glass and in wooden 

 boxes or flats, which they state was necessary in their climate, and 

 assumed that such plants compare in reaction with similar plants 

 grown in the field. The use of a photometer would have shown 

 this assumption to be unwarranted, as fully 50 per cent of the light is 

 removed in a greenhouse with clean panes. In the case of panes 

 only lightly frosted, it is probable that less than 15 per cent of the 

 light incident actually reached the plants. As their experiments 



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Fio. 1. Three plants of alfalfa series 14, stripped for 27, 17, and 11 hours respectively, showing 

 that the loss of a few leaves does not affect the stomatal movement. 



were carried out with a view of discovering the effect of light upon 

 the stomatal movement of their plants, they can apply only to plants 

 grown under similar conditions as to light intensity. With plants 

 growing in a desert, water is the factor which determines their exist- 

 ence. In shade, even if only partial, the determining factor is 

 light; hence, in experiments conducted as were theirs, it is to be 

 expected that the stomata would respond to light much more quickly 

 than to any other factor. Moreover, their terms "light," "hazy," 



