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On the Function of Silica in the Nutrition of Cereals. — Part I. 

 By A. D. Hall and C. G. T. Morison. 



(Communicated by Professor H. E. Armstrong, F.E.S. Received December 22, 

 1905,— Read February 1, 1906.) 



(From the Lawes Agricultural Trust Committee.) 

 1. Introduction. 



The presence of silica in plants was first demonstrated by the analyses 

 of De Saussure,* who pointed out that the Gramineae were particularly 

 distinguished by the large proportion of this constituent present in their 

 ash. Liebig, who classified plants as " silica plants," " lime plants," and 

 " potash plants " according to the predominance of one or other of these 

 constituents in their ash, in accordance with his " mineral theory," regarded 

 the silica as a necessary element in plant nutrition. This view led Wayf 

 to introduce as a cereal manure a rocky material derived from the Upper 

 Greensand near Farnham, which contained a considerable proportion of 

 silicate easily soluble in acids. But when SachsJ succeeded in maturing 

 maize plants in water cultures containing no silica, whereby the proportion 

 of silica in the ash of the mature plant was reduced from the normal 20 per 

 cent, or so to as little as 0'7 per cent., it became evident that silica could 

 no longer be placed in the same category as phosphoric acid and potash as 

 essential elements of plant nutrition, and Jodin§ raised four successive 

 generations of maize in water cultures without any supply of silica beyond 

 that contained in the original seed. 



Other investigators again showed that the stiffness of cereal straw, 

 which had been attributed to the presence of silica, depends on the develop- 

 ment of the internodes under the influence of such factors as illumination 

 and exposure. 



Henceforward little or no importance seems to have been attached to the 

 presence of silica, yet, as the following ash analyses show, it forms a constant 

 and considerable proportion in the ashes of certain plants, though it is 

 almost absent from the majority. 



* 'Recherches snr la Vegetation,' Paris, 1804. 

 t ' Roy. Agric. So-. Journ.,' vol. 14, 1853, p. 225. 

 % ' Flora,' 1862, p. 52. 

 § ' Ann. Agron.,' vol. 9, 1883, p. 385. 

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