344 University of California rublications in Agricidtural Sciences [Vol. 1 



The Use of Sand as a Culture Medium 



The ease with which solutions can be prepared and subse- 

 quently analyzed has made the water-culture method especially 

 desirable in investigations of the role of nutrient substances in 

 plant growth. A solution has generally been recognized, how- 

 ever, to be otherwise undesirable as a medium for the growth of 

 the higlier plants, since tlie root system is kept, during the course 

 of the experiment, in an unnatural enviionment. Thus, while 

 this method serves admirably for analytical purposes, it seems 

 probable that the plant thus subjected to an unnatural environ- 

 ment will suffer certain more or less serious physiological dis- 

 turbances. In this connection, it is a well-established fact that 

 the development of root hairs is much greater in sand than in 

 water," the resistance of the substratum favoring root-hair pro- 

 duction.^- Roots in general grow longer and thinner in water 

 than in sand or moist soil. Hall. Breuchley, and Underwood^^ 

 think that the more vigorous growth of barley in sand, as com- 

 pared with water cultures, is due to more efficient aeration of the 

 former. It would seem, therefore, that sand is preferable to 

 water as a culture medium, since in sand cultures the physical 

 conditions present about the root system more nearly simulate 

 those found in the soil. It is still a question just what part these 

 physical conditions may have in j^lant nutrition. Undoubtedly 

 such physical reactions as capillarity" and adsorption^^ must be 

 important factors, since both the absorption and availability of 

 nutrient salts would be affected by tliese physical phenomena. 

 Breazeale^'' has shown that the effect of concentration in sand 

 cultures is very different from that in water cultures, the best 

 concentration for wheat in water being three hundred parts per 

 million, while in sand it is in the vicinity of two thousand five 

 hundred parts per million, an effect which is no doubt largely due 

 to the adsorption of certain salts or ions by the sand particles. 



11 Schwarz, Bot. Inst. Tubingen, vol. 1, pp. 1.55-188, 1883. 



12 Snow, Bot. Gaz., vol. 40, pp. 12-43, 1905. 



13 Loc. cit. 



1* Bell and Cameron, Jour. Phys. Cheni., vol. 10, p. 659, 1906. 

 15 Schreiner and Failyer, U. S. Dept. Agric. Bull. 32, 1906. 

 i« Breazeale, Science, n. s., vol. 22, pp. 146-149, 1905. 



