Factors Affecting Growth and Reproduction 207 



gardens with slat frames so as to approximate the intensity of 

 hght found in the woods where ginseng grows wild. Tea, a 

 leaf product, attains its best quahty and yield in the shade 

 of taller trees purposely planted in alternate rows with the 

 tea plants. 



The influence of sunhght and moisture may also be seen in the 

 geographic distribution of the flax crop. Flax is grown for two 

 distinct products: one, the bast fibers (a vegetative part), used 

 in making hnen thread ; and the other, the seed (a reproductive 

 structure), used in manufacturing Hnseed oil. The leading 

 centers of fiber production are in northwestern Russia, northern 



^ 



..u 



^ ■ ^*A\r^ 



Short day 



Short day 



Long day 



Long day 



Figs. 122 and 123. Figure 122 shows, on the right, an apple seedling that grew more 

 rapidly with 10 hours' daily illumination than, the control plant on the left with a full 

 day's illumination. In contrast, the maple seedlings {Acer negimdo), shown on the left in 

 Figure 123, were dwarfed and forced into dormancy by shortening the illumination period to 

 10 hours, while the plant exposed for the full length of day grew rapidly. The photograph 

 of the apples was made July 13 and that of the maples September 22. 



These photographs show clearly that light has effects other than those of photosynthesis 

 on plants, and that its effects are different on different plants (Garner and Allard. u. S. D. A.) 



