THE ASH OF PLANTS. 189 



the water-plants than in the garden-plants, as shown by the 

 subjoined figures. {Vs. St., Y, p. 132.) 



JPei' cent of ash in 



Stems and Leaves. Soots. Seeds. Entire Plant. 



Water-plant 18.6 15.3 2,6 16.7 



Garden-plant 8.7 6.8 3.4 7.1 



We have seen that well-developed plants contain a 

 larger proportion of ash than feeble ones, when they grow 

 side by side in the same medium. In disregard of this 

 general rule, the water-jjlant in the present instance has 

 an ash-percentage double that of the land-j)lant, although 

 the former was a dwarf compared with the latter, yielding 

 but "|„ as much dry matter. The seeds, however, are 

 scarcely different in composition. 



Disposition by tbe Plant of excessive or superfluous 



asll*iugredients. — The ash-ingredients taken up by a plant 

 in excess beyond its actual wants may be disposed of in 

 three ways. The soluble matters — those soluble by them- 

 selves, and also incapable of forming insoluble combina- 

 tions with other ingredients of the plant — viz., the alkali 

 chlorides, sulphates, carbonates, and j)hosphates, the 

 chlorides of calcium, and magnesium, may — 



1,, Remain dissolved in, and diffused throughout, the 

 juices of the plant ; or, 



2., May exude upon the surface as an efflorescence, and 

 be washed off by rains. 



Exudation to the surface has been repeatedly observed 

 in case of cucumbers and other kitchen vegetables, grow- 

 ing in the garden, as well as with buckwheat and barley 

 in water-culture. ( Fs. St., VI, p. 37.) 



Saussure found in the white incrustations upon cucum- 

 ber leaves, besides an organic body insoluble in water 

 and alcohol, chloride of calcium, with a trace of chlo- 

 ride of magnesium. The organic substance so enveloped 

 the chloride of calcium as to prevent deliquescence of 

 the latter. [Becherches sur la Yeg., p. 265.) 



Digitized by Microsoft® 



