264 JOUKNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



seeds by rapid twisting and turning movements. These hairs are figured 

 on plate 2. G. F. S.-E. 



Influence of Gaslight. 



Plant Growth, A Study of the Effect of Incandescent Gas- 

 light on. By L. C. Corbett (West Virginia Agr. Exp. St., Morgantown, 

 W. Va, Bull. 62, p. 79 ; 1899). 



After referring to previous observers the author considered that the 

 quality and intensity rather than the manner of making the artificial 

 light should be investigated. Hence he commenced in 1895 to test the 

 influence of the Welsbach incandescent gaslight upon various plants 

 growing in greenhouses. Experiments were continued up to 1899. 



In no case was the artificial light found to be a satisfactory substitute 

 for daylight. 



Lettuces were first grown in two houses, some under normal con- 

 ditions, the others subjected to incandescent light at night only. Two 

 methods were tried — raising plants in pots and transplanting them to the 

 stage (the house), and sowing the seed. These latter grew too tall with- 

 out making a sufficient spread of leaves to give the greatest weight for 

 the area occupied. Photographs and nine charts illustrate two important 

 factors in the behaviour of the plants : the plants near the light — eight 

 lights being all at one end — show a much greater growth than those near 

 the other end of the house. A less marked variation is shown in the 

 curve of growth of the plants in the normal section made at the same 

 time. The light house thus shows in a marked way the influence of the 

 lamp upon the plants near by as well as suggesting the range of its 

 influence. 



The advantages of the light were corroborated by weights. Thus the 

 weight of 400 plants in the light area was 68*56 lb., and in the normal 

 49*428 lb. The plants had been under the influence of the light forty- 

 six nights. During that period the lamps were turned on at 5 o'clock p.m. 

 and extinguished at 7.15 next morning, thus making 655*5 hours that the 

 plants were actually exposed to the stimulus of the light, against 448*5 

 hours that they were in normal conditions. Hence the plants exposed 

 to the gaslight exceeded those normally grown by 38*7 per cent, of the 

 total weight of the plants in the normal house. 



To test the rapidity of growth the auxanometer was used, with the 

 result that during twenty- four hours was the more rapid rate of growth 

 of the light-house plants. The light plant was found to grow \\ inch 

 more in eight days than the normal plant. 



With regard to the most active period of growth for the plant in the 

 light section, it began at 11 p.m. and continued to 9 a.m. ; while during 

 the same space of time the normal plant gave an active growth period 

 beginning at 4 a.m. and continuing until 11 a.m. Hence in the case of 

 the light plant the period was ten hours, while in the normal house the 

 period was seven hours. 



With regard to Radishes grown between the rows of Lettuces a very 

 slight advantage as to the size of the roots appeared as the result of the 

 incandescent light. As to Spinach no plant used responded more to the 

 stimulating influence of the gaslight. 



