150 THE PRINCIPLES OF FLORICULTURE 



By means of chemical substances which are quickly 

 acted upon by light rays a series of observations were 

 carried on to determine the relative values of morning 

 and afternoon light. These are recorded in this bulletin 

 on previous page. 



" The experiments shown in Table I, which lasted one 

 year with practically no interruption, were made in a green- 

 house twelve by forty feet, running east and west. This 

 was an even-span house with the usual roof slope (30), 

 and was about eighteen years old. Eight years before 

 these records were made, it had been remodeled and 

 glazed with No. 2 double thick greenhouse glass, 16 X 24 

 inches. The sides had the original glass, about 12 X 22 

 inches. The light records were taken from 9 A.M. to 12 M. 

 and from 12 M. to 3 P.M. at a point about four feet from 

 the roof, and five feet from the south end of the house, 

 and in all cases showed a greater percentage of light for 

 the morning than the afternoon ; the average for year, 

 based on monthly averages, being 10 per cent in favor of 

 the morning light. The greatest difference is shown in 

 November and December, where the percentage (daily 

 average) is 20 and 27 respectively; while the smallest 

 difference (only .9 per cent) is shown in January." 



