2o8 General Botany 



France, Belgium, and Ireland, in regions of low light intensity 

 and high humidity. The northern plains from Minnesota to 

 Alberta, northern Argentina, Japan, Italy, and India are the 

 centers of seed production, all of these being regions of low 

 humidity and high Kght intensity during the season when the 

 crop is grown. 



Intense light favors the development of reproductive struc- 

 tures. The production of flowers, fruits, and seeds is promoted 

 by bright sunshine, provided there is sufficient soil moisture to 

 permit normal growth of the plant. Our greatest grain and fruit 

 producing areas are in regions where these conditions prevail : 

 the Middle Western states, Washington, California, and Colorado. 

 In some of the areas the water supply is maintained by irrigation, 

 and the intensity of the hght is but slightly reduced by clouds or 

 atmospheric moisture during the growing season. 



It is a common observation that partial shade reduces flower 

 production, and one of the difficulties in producing flowers in 

 greenhouses in the winter time is the low hght intensity. Keeping 

 greenhouse glass clean at this season is as important as providing 

 favorable temperatures. 



In regions of intense light (Colorado, for example) many fruit 

 trees blossom and set fruit every year, while the same varieties, 

 in regions of less light, fruit only once in two or three years. In 

 wet seasons in the Southeastern states the yield of cotton fiber and 

 cotton seed per acre is greatly reduced, although the plants grow 

 to more than normal size. 



The most brilliant wild flowers occur in alpine meadows, where 

 the light is intense and the moisture always sufficient. The 

 flowers also are larger, although the plants are smaller than those 

 of the same species growing at low altitudes. 



Length of day. The length of the day is an important factor 

 in determining the flowering and reproduction of some plants. 

 For example, ragweeds given 7 hours of light daily blossom 2 

 months earher than similar plants exposed for 14 hours daily. 



