372 



Journal of Agricultural Research 



Vof. XV. No. 7 



are given in percentages of the total ash. In Table II the total ash, and 

 likewise the constituents, are calculated in percentages of the dry weight 

 of the plant material. 



Table II. — Ash constituents of healthy and diseased spinach plants 

 [Calculated as percentages of dry weight] 



While the quantity of total ash is not strikingly different in normal 

 and in diseased material, the normal tops in all cases seem to be a little 

 richer than the diseased tops, whereas the roots of the diseased plants 

 have somewhat more ash than the normal roots. The great excess of 

 ash in the leaves over the roots is in agreement with the general rule 

 and is seen in both kinds of material. 



It is interesting to note that spinach leaves have been found by others 

 to contain an unusually large quantity of total ash, belonging in the 

 same class as tobacco leaves {Nicotiana tabacum), hop leaves {Humulus 

 lupulus), head lettuce {Laciuca saliva), forage-beet tops {Beta vulgaris) 

 and Elodea canadensis in containing from 16.4 to 20 per cent of total ash. 

 Wolff (49, p. 141-150) reports the average for spinach to be 16.48 per 

 cent. The writers find the average of normal samples taken from two 

 fields to be 20.4 per cent, the blighted 17.45 per cent. Thus, the tops of 

 the normal plants are markedly richer in total ash than are those of the 

 diseased plants. This relation is reversed in the roots, the blighted 

 plants averaging 9.14 per cent, in comparison with 7 per cent in the normal 

 material. 



Concerning the individual constituents present, a number of points are 

 worth noticing. The case of the silica content is one of especial interest. 

 Although all usual precautions were taken to remove adhering soil, the 

 silica present makes up one of the chief components of the ash, both in 

 leaf and root. As may be seen in Table II, the tops contain several times 



