8 



EFFECTS OF ARTIFICIAL SHADING ON PLANT GROWTH. 



character and in indicating the minimum amount of solar energy re- 

 quired by these plants. 



Six different plants and six different degrees of light intensity were 

 used in the present experiments, which were so planned as to minimize 

 the influence of the resulting changes in physical conditions other 

 than light. 



EXPERIMENTAL METHODS. 



Two beds, A and B, 6 by 24 feet each, were prepared for seeding. 

 On April 2, 1908, one row each of the following six plants was planted 

 in each bed: Kadish, French Breakfast; lettuce, New Orleans Improved 

 Passion; potato, Triumph; cotton, Lee's; corn, St. Charles Red Cob; 

 mustard, Bloomdale White. 



As soon as the seedlings began coming through the soil each bed 

 was covered with a framework over which cloths of different texture 



LF7Tt/C£ 



COPAT 



COTTOA/ 



POTATO 



W(/ST/IPD 



BSD 



12 3 4 5 6 



PADiSH 



LETTUCE 



COPM 



COTTON 



POTATO 



MUSTAPD 



BED B 



Fig. 1.— Diagrams of the beds and plantings. 



(PI. I, iig. 2) were stretched so as to give five different degrees of 

 shades, the sixth section being left uncovered so as to receive full 

 light. Each shade was 4 feet wide and was slightly inclined, resting 

 about 2 feet above the beds on the south side and 2\ feet above them 

 on the north side. The beds had the long dimension east and west 

 and were closed by boards on the sides and on the ends. The diagram 

 (fig. 1) shows the arrangement, and the general appearance of the beds 

 is shown in Plate I, figure 1. 



Section 1 (east end) received the deepest shade and section 6 (west 

 end) was left open to the full light. Since the shades were not 

 separated by partitions, it will be seen that a small portion of the bed 

 between each two shades was under the next deeper shade in the 

 morning and under the next lighter shade in the afternoon. The 

 result was that only the center of each section received the character- 

 istic light reduction afforded by the corresponding shade, and there 



279 



