430 



Plant Physiology 



fruit-bearing plants containing objectionable flavors might 

 be improved by reduced light. 1 



262. The effect of shading upon other environmental 



B 



FIG. 121. Bark of Acer Pseudo-platanus ; epidermis (ep), periderm (pr), 

 primary cortex (pc) ; developed in white light (A) and in red light (B). 

 [After Teodoresco.] 



factors. - - From the preceding statements it has been noted 

 that half-shade may modify in a direct manner other condi- 

 tions of the environment. The factors commonly affected 

 are the following : (1) moisture conditions of the soil ; 

 (2) rate of evaporation ; (3) humidity ; (4) temperature ; 

 (5) air movement; and (6) certain biological relations. 



The tables on the next page indicate the effect of the 

 usual shade tent (made of unbleached cotton) upon soil 

 moisture and evaporation (first table after Whitney). 



Much remains to be determined respecting the modifica- 

 tions in plants induced by shading, and likewise exten- 

 sive studies are required to evaluate the different factors 

 involved. From the indications already presented, it is 



1 Schuebeler, Bonnier, and Flahault have shown that in northern 

 climates flowers are more highly colored and plants commonly richer in 

 essential oils. It is also well known that plants rich in volatile oils and 

 other aromatic products are numerous in the Mediterranean region, a 

 region in which the rainy season is confined largely to the winter months, 

 and the summer is practically a continuous exposure to intense sunlight 



