96 Plant Physiology 



(1) Reduced surfaces, such as in cactus, aloe, and many 

 desert plants. 



(2) Reduction in number of stomata, as in many grasses 

 and sedges. 



(3) Sinking of stomata in special epidermal cavities as 

 in yucca and carnation. 



(4) Thickened cuticle, as in carnation, pine, many desert 

 plants, and the like. 



(5) Production of a waxy bloom upon the cuticle, as 

 in cabbage, sugar-cane, and wheat. 



(6) The development of hairs upon the leaves, as in 

 mullein and numerous mountain plants. 



(7) The possession of water-storage tissues, as in many 

 desert plants, begonia, etc. 



57. Conditions affecting transpiration. - The condi- 

 tions of the atmosphere greatly affect the evaporation from 

 a water surface or from any other surface. In dry, hot 

 weather, hay is quickly made and cured. The " pull ' 



of the atmosphere upon all 

 moist surfaces results, there- 

 fore, in a prompt loss of water. 

 In the same way transpira- 

 tion in a healthy plant is ob- 

 viously influenced by condi- 



FIG. 29. From a stalk of sugar tions^of the airland it is to a 

 cane, epidermal region and certain extent influenced by 



conditions of the soil. In gen- 

 eral, the important air fac- 

 tors are humidity, temperature, wind velocity, and light. 

 Low humidity, high temperature, rapid movement of the 

 wind, and intense light commonly facilitate transpiration 



