PHYSICAL AND METEOROLOGICAL RESEARCHES. 



107 



0.28 meter, while those in the red hothouse readied 0.5 meter. A 

 photograph taken October 12, 1896 (fig. 3), shows the differences in 

 growth under similar temperatures. It will be noticed that the sensi- 

 tive plant in the white hothouse had gained in stockiness what it bad 

 lost in height. Indeed, the diameter of the stem and the surface of 

 the leaves were larger in the plants in the white hothouse than in 

 those in the red. The weight of the above-ground part of the plants 

 of the different hothouses was as follows: 



Effect of different colored lights on the iveiglit of sensitive plants. 



It will be seen that, notwithstanding the great height of the sensi 

 tive plant grown under red glass, its weight is about half that of the 

 plant grown in the white hothouse. 



In experiments with other plants results were obtained which differed 

 somewhat according to the species. The results with Strobilantlies 

 dyerianus agreed entirely with those for the sensitive plant. 



Young summer lettuce was placed in different hothouses during 

 June and July. The results in the white hothouse and in the open air 

 were identical. The leaves were large, thick, of a reddish-brown color, 

 and formed a well-rounded head. The lettuce in the red house was 

 drawn, the leaves were long and straight, blanched, drooping, and 

 widely separated by long internodes. The plants in the green house 

 increased in height a little, while the leaves were less curled than those 

 in the red house. The lettuce in the bine house added only a few leaves, 

 without growing at all in height. The height attained by the different 

 plants was as follows: In the red house, 1.5 meters; in the white, 0.6 

 meter; in the green, 0.4 meter; in the blue, 0.1 meter. The lettuce in 

 the red house bloomed 15 days earlier than that in the white house. 

 Figure 1 (p. 108) shows these differences. 



In the experiment with maize, young stalks measuring 0.15 meter in 

 height were set out in the hothouses in May. They were measured 

 July 22 with the following results: In the white hothouse, 1 meter; in 

 the red, 0.4 meter; in the green, 0.2 meter; in the blue, 0.15 meter. 

 These results differ from those observed in the case of the sensitive 

 plants in that the development of maize was less in the red hothouse 

 than in the white. 



In the experiments with peas and beans the most vigorous growth 

 occurred in the white hothouse. There was less development in the 

 red, and the minimum of growth was obtained in the blue hothouse. 



