40 



the plants, the vahdity oi the conehision is ])ix)bably not affected by 

 the firet assumption. 



The second assumption upon which the conchision is based, 

 namely, that the plants which have made the better growth have an 

 ash composition more nearly approacliing the optimum, is subject to 

 considerable doubt because of our imcertainty concerning the factois 

 and laws governing the ash composition of plants in general. A 

 glance at a collection of ash analyses of the same plant shows that 

 the same plant grown under different conditions may make practi- 

 cally the same growth and yet have a very different ash composition. 

 It does not necessarily follow, however, that under like conditions of 

 growth the ash compositi(ju of a plant can be varied without affecting 

 the growth. 



Some of the conditions afl'ectuig the ash composition of plants are 

 known, and among these may be enumerated the following : The 

 humidity, intensity of hght, temperature, and all those conditions 

 which may be summarized as clunate, the water content of the soil,' 

 the character of the soil,- the fertilizers applied,^ the stage of maturity 

 of the plant,' and a great number of circumstances, such as the culti- 

 vation of the soil, the thickness of tlie stands,^ and the time of plant- 

 ing," wliich affect either the chmatic or soil conditions. All these 

 factoi-s, of course, do not affect the ash composition independently, 

 but more or less mterdepenilently, and therefore it is somewhat tliffi- 

 cult to isolate and measure the effect of one factor. However, from 

 the studies that have been made, it appeal's that climatic influences 

 have the greatest eff'ect on the organic and inorganic composition of 

 the plant.' 



It seems probable that for every set oi climatic conditions there is 

 an optimum ash composition of the plant; and that when the ash 

 composition is varied from this optimum, by varying the chemical 

 character of the soU, the amount of nutrients available, etc., the 

 growth is aff'ected. If this is so, variations in the ash composition 

 of plants induced by differences in the character of the sod, under 

 otherwise like conditions of growth, are significant. But variations 



' Fittbogen, J., Landw. Jahrb., 2 (1873), p. 353. Langer, L., and ToUens, B., Jour. Landw., 49 (1901), 

 p. 209. Daszewski, A. von, and Tollens, B., Jour. Landw., 48 (1900), p. 223. Wilms, J., and Seelhorst, 

 C. von, Jour. Landw., 46 (1898), p. 413. 



2 Hall, A. D., Jour. Soc. Arts |London], S2 (1904), p. 881; Jour. Agr. Sci. [England], 1 (190.5), No. 1, pp. 

 65-S8. Stahl-Schroder, M., Jour. Landw., 52 (1904), p. 193. 



3 Kellner, O., et al., Landw. Vers. Stat., 39 (1891), p. 36L Dikow, A. von, Join. Landw., 39 (1891), p. 

 134. Atterberg, A., Jour. Landw., 49 (1901), p. 97. 



* Tucker, G. M., and Tollens, B., Jour. Landw., 48 (1900), p. 39. HaielhoU, E., and Wemei, S., Landw. 

 Jahrb., 44 (1913), No. 4, p. 651. Fliche, P., and Grandeau, L., Ann. Chim. et Phys., 5. ser.,8 (1876),p.4S6. 

 Wilfarth, II., Romer, H., and Wimmer, G., Landw. Vers. Stat., (Vi (1905), No. 1-2. 



'Seelhorst, C. von, and Panaotovic, Jour. Landw., 47 (1899), p. 379. Atterberg, A., Jour. Landw., 49 

 (1901 ), p. 97. 



' Stahl-Schroder, M., Jour. Landw., 62 (1904), p. 31. 



' Lawes, J. B., and Gilherf, J. II., Jour. Chem. S(x;. |I,ondon], 45 (1S84), p. 305. Stahl-Schriider, M., 

 Jour. Landw., 52 (1904), p. 193. 



