THE ASH OF PLANTS. 189 
the water-plants than in the garden-plants, as shown by the 
subjoined figures. (Vs. St., V, p. 182.) 
Per cent of ash in 
Stems and Leaves. Roots. Seeds, Entire Plant. 
Water-plant..... 18.6 15.3 2.6 16.7 
Garden-plant.... 8.7 6.8 2.4 eke 
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-plant in the present instance has 
an ash-percentage double that of the land-plant, 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 the Plant of excessive or superfluous 
ash-ingredients.—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 phosphates, 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 
. m water-culture. (Vs. S¢t., VI, p. 37.) 
Saussure found in the white incrustations upon cucum- 
ber leaves, besides an organic body insoluble in water 
and aleohol, chloride of calcium, with a trace of chlo- 
ride of magnesium. The organic substance sc enveloped 
the chloride of calcium as to prevent deliquescence of 
the latter. (Recherches sur la Veg., p. 265.) 
