426 Plant Physiology 



of many forest trees. A thorough study of the relations 

 of seedling trees to half-shade operations is greatly to be 

 desired in the advancement of forestry work generally. 



Many bush fruits and other agricultural products are 

 commonly grown in the partial shade of other plants. It 

 is generally believed that currants are benefited by the 

 partial shade of grapes or certain tree-fruits, provided the 

 water-content of the soil is not seriously affected. Coffee 

 and tea are more profitably produced in subtropical regions 

 in forest glades, or when partially shielded by occasional 

 trees. In southern Algeria and other portions of the Sa- 

 hara shading is practiced on a large scale in the oasis cul- 

 tures. The protecting palms improve the conditions for 

 figs, peaches, and other fruits, under which, in turn, vege- 

 tables may be grown, provided only that the water-supply 

 is adequate. On the other hand, the production of grapes, 

 with higher sugar content for wine purposes may require a 

 selection of slope insuring best exposure to light during a 

 certain period of growth and maturity. Fruit trees are 

 grown on the southern sides of walls in England and 

 France, and it would appear that both the additional light 

 and heat thus obtained are advantageous. 



In many parts of the United States, especially in the 

 Central West, lettuce and other salad crops become bitter 

 and undesirable for table use with the stronger light and 

 heat of the summer season. The shade tent, properly 

 employed, will permit the constant summer culture of 

 such crops. The strong flavor of radishes produced dur- 

 ing the summer are also modified and improved by partial 

 shade. 



260. Morphogenic effects. - The comparative effects 



