8 PHYSIOLOGY OF NUTRITION. 



above, is represented in Fig. 2. In a vessel arranged as above, 

 which contained only about 5 litres of water, I brought a 

 Phaseolus plant to splendid development. A complete renewal 

 of the food solution was not made from the commencement of the 

 experiment till the time of flowering, when the plant was above 

 the height of a man. I often found that in my laboratory, where 

 Maize grew vigorously, that beans did not develop normally. 

 Relatively dry air and the products of combustion of gas appear 

 to influence the growth of beans far more injuriously than, e.g., 

 that of the Maize ; the former consequently must always, when 

 a plant house is not available, be cultivated in the open air out- 

 side the window. 



An excellent object for water cultures intended for purposes of 

 demonstration is the willow. For example, early in February, 

 1894, I introduced into the cover of the 5 litre culture cylinder a 

 branch of Salix fragilis, about 25 cm. long and 2 cm. in diameter. 

 The vessel contained at first only spring water, in which the 

 branch was immersed to half its length. Over the portion rising 

 above the cover was placed a glass cylinder. At the end of four 

 weeks the buds began to burst, and the roots had already become 

 fairly long. The glass cylinder was now removed, and the spring 

 water in the culture vessel was replaced by food solution (half 

 strength). At the end of the next four weeks food solution of the 

 usual strength was put into the culture vessel. Every day the 

 evaporated water was replaced, and every two months the food 

 solution was renewed. In the course of the summer a vigorous 

 root system developed, and six long, branched, very woody, 

 perfectly normal lateral branches with numerous leaves. During 

 the summer the plant was often placed in the open air outside the 

 window. At the beginning of September the food solution was 

 replaced by spring water ; the plant was kept in a warm room 

 behind a window looking to the south. It cast its leaves quite 

 gradually from the middle of October to the end of December, 

 and now (January 10, 1895) is still in a state of winter dormancy. 



1 ^Respecting suitable plant houses see Wolff, Versuchsstationen, Bd. 8, p. 

 485 ; and Nobbe, idem, Bd. 12, p. 477. 



2 Gasholders are to be obtained from K. Muencke, Berlin, Luisenstr. 58. 

 The Wasserstrahlgeblase, also to be obtained from Muencke, are likewise very 

 convenient for passing air ; they can be attached in the simplest manner to 

 the water supply. See Muencke's Catalogue, 1886, Pt. 1, p. 76. 



8 See Wortmann, Botan. Zeitung, 1892. 



