BOTANY. 191 



Plants gifown under different colored glass {Gard, Chron., 16 

 {1894), ser. ■>, p. 130). — 'SI. Villon is reported us having just concluded 

 a series of experiments on the cultivation of plants under colored glass. 

 Plants were potted in cases in which the panes of glass could be easily 

 replaced by others of different shades. The following kinds of colored 

 glass were used: (1) Glass made orange color by a coating of bichromate 

 of potash^ allowing only the yellow and red rays to pass through; (2) 

 violet glass colored with manganese, which absorbs the yellow and blue 

 rays of the spectrum; (3) blue glass colored with cobalt, allowing only 

 the red and ultra-violet rays to pass ; (4) blue glass colored with copper, 

 allowing only the ultra-violet rays to pass and absorbing the extreme 

 red rays; (5) glass covered with a thin layer of silver, allowing only 

 the blue rays to pass; (6) uranium glass, absorbing the light to a great 

 extent; (7) gilded glass; (8) glass colored red with protoxid of copper, 

 absorbing all the colors of the spectrum between red and blue; and (9) 

 glass colored green with protoxid of iron, absorbing the red rays. 



Taking the growth of the plants under white glass as 100, the fol- 

 lowing results were obtained: 



Comparative (jrowtk of plants under glasSi 



Under orange glass .... ^ ... ^ 150 



violet glass 150 



cobalt blue glass .... ^ .... ^ . . 140 



copper bine glass 120 



^vliite glass ^ 100 



Under silvered glass 66 



uranium glass 40 



gilded glass 40 



red glass .......... ^ .. 15 



green glass ............. . . 10 



These experiments show that the light that favors ^'egetatiou most 

 is the orange light of the chromic glass and the violet of the manganese 

 glass, and as the radiations that these glasses allow to pass are the 

 red and violet, these rays are the ones that seem to be most favorable 

 to the development of plants. However, the growth under no glass at 

 all, wherever possible, is decidedly the best of all. 



The formation and decomposition of organic acids by the higher 

 plants, K. PuRJEWicz {Kiew : 1893, p. 90, tabid; uhs. in Bot. Centbl., 58 

 il894), No. 11, pp. 368-37-1). — The author gives in an introductory chap- 

 ter a review of the extensive bibliography of this subject. The paper 

 itself is divided into three parts, as follows: (1) Decomposition of the 

 acids, (2) their formation, and (3) the gas exchange brought about by 

 both processes. 



The author found that decomposition of the organic acids in i^lauts 

 takes place (1) under the influence of light, (2) a higher temperature^ 

 and (3) by constantly keeping in the dark at the ordinary temperature. 

 He investigated 24 species of phanerogams and found the decomposi- 

 tion in light was constant. Also in etiolated plants and chlorophyll- 

 free parts the same process takes place. He found the roots of Phase- 

 olus in 5 hours had their acidity decrease from 67 to 00 per cent, and 

 in etiolated germinating wheat plants there was a decrease of 8 points 



