Winifred E. Brenculey and Kharak Singh 199 



differences in behaviour manifested themselves which demanded closer 

 investigation. 



Between May 7th and June 25th, 1920, the following conditions 

 prevailed : 



Average weekly maximum temperature 27-35° C. 

 ,, ,, minimum „ 8-13° C. 



Total hours of sunshine (per week) ... 49-3-65-7 

 Daily average hours of sunshine ... 8-4 



It was soon evident that the crowded plants were making the better 

 growth; they were larger and greener than the spaced plants, some of 

 the latter becoming yellowish, with leaves that inclined to shrivel. The 

 crowded peas maintained their apparent lead, and when cut were mostly 

 healthy and green, with only four casualties, whereas many of the spaced 

 plants were pale in colour and 15 out of the 64 had succumbed. 



The effect of competition was evident in the crowded square, as the 

 outer plants averaged 2'127±-065 gm. and the average of the inner ranks 

 varied from 1-523 ± -185 to 1-686 ± -058. The spaced plants, however, 

 failed to demonstrate the advantage of the extra light they had received, 

 as their mean weight was only 1-912 ± -042 gm., less than the outer rank 

 of the crowded set. 



A marked difference was noticeable between the plants in the spaced 

 set. Those which were green and healthy had good stiff roots studded 

 with rather outstanding sturdy laterals, whereas in those in which the 

 upper leaves were turning pale the roots looked unhealthy and brown, 

 and were flabby and incHned to be slimy. The worse the shoot the worse 

 the root. The green healthy plants were of the normal type, with one tall 

 shoot and large dark green leaves, whereas those with pale shoots were 

 bushy at the base, owing to the development of axillary buds. This was 

 apparently due to an effort to overcome some detrimental factor acting 

 upon the spaced peas and preventing them from developing normally, 

 for in the earher experiments with barley the crowded plants also ap- 

 peared to make the larger growth on the whole, but were not so heavy 

 as the spaced plants when cut. Even the outer rank of the crowded 

 plants showed the influence of this adverse factor to some extent, as the 

 mean weight was not very much above that of the inner plants which 

 were under the influence of more light competition. As in the first 

 experiment described the plants wnthin the square were all very similar 

 in growth and weight. 



The harmful effect w^as obviously due to the prevailing high tempera- 

 tures or the excessive power of the sun's rays, or both, but the relative 



