THE ASH OF PLANTS. 199 



The recommendation to supply silex to grain crops, in 

 order to stiffen the straw and prevent falling of. the crop 

 before it ripens, either by directly applying alkali-silicates, 

 or by the use of fertilizers and amendments that may 

 render the silica of the soil soluble, must, accordingly, be 

 considered entirely futile from the point of view of the needs 

 of the crop, as it is from that of the resources of the soil. 



Chlorine. — As has been mentioned, both Nobbe and 

 Leydhecker found that buckwheat grew quite well up to 

 the time of blossom without chlorine. From that period 

 on, in absence of chlorine, remarkable anomalies appeared 

 in the development of the plant. In the ordinary course 

 of growth, starch, which is organized in the mature leaves, 

 does not remain in them to much extent, but is transferred 

 to the newer organs, and especially to the fruit, where it 

 also accumulates in large quantities. In absence of chlo- 

 rine, ill the experiments of Nobbe and Leydhecker, the 

 terminal leaves became thick and fleshy, from extraordinary 

 development of cell-tissue, at the same time they curled 

 together and finally fell off, upon slight disturbance. The 

 stem became knotty, transpiration of water was suppress- 

 ed, the blossoms withered without fructification, and the 

 plant prematurely died. The fleshy leaved were full of 

 starch-grains, and it apjieared that in absence of chlorine 

 the transfer of starch from the foliage to the flower and 

 fruit was rendered impossible ; in other words, chlorine (in 

 combination with potassium or calcium) was concluded to - 

 be necessary to, was, in fact, the agent of this transfer. 

 Knop believes, however, that these phenomena are due to 

 some other cause, and that chlorine is not essential to the 

 perfection of the fruit of buckwheat, (see p. 182). 



Iron. — We are in possession of some interesting facts, 

 which appear to throw light upon the function of this 

 metal in the plant. In case of the deficiency of this ele- 

 ment, foliage loses its natural green color, and becomes pale 

 or white even in the full sunshine. In absence of iron a 



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