The Light Relation 



425 



ditional incentive to the 

 use of any device which 

 may regulate or control 

 the conditions of the en- 

 vironment. 



259. Crops responding 

 to half-shade. - - In gen- 

 eral half-shade increases 

 succulence and delicacy, 

 so that it is particularly 

 applicable to such crops 

 as asparagus, cauliflower, 

 celery, lettuce, and rad- 

 ish. It is employed in 

 forcing rhubarb, in the 

 cultivation of ginseng, 

 and has proved especially 

 important in pineapple 

 culture in Florida. 

 Sumatra tobacco, grown 

 for wrapper purposes in 

 the Connecticut valley 

 and in other regions, has 

 been greatly improved by 

 half-shade conditions. 

 Half-shade is also neces- 

 sary in many cases to 

 the maintenance of 

 proper conditions for seed 

 beds, and it is essential in 

 the nursery propagation 



FIG. 118. Peas grown 6 days in dark- 

 ness (a), in about s light (6), and open 

 in greenhouse (c). 



