190 HOW CROPS GROW. 
Saussure proved that foliage readily yields up saline 
matters to water. He placed hazel leaves eight successive 
times in renewed portions of pure water, leaving them 
therein 15 minutes each time, and found that by this treat- 
ment they lost ‘|,, of their ash-ingredients. The por- 
tion thus dissolved was chiefly alkaline salts; but con- 
sisted in part of earthy phosphates, silica, and oxide of 
iron. (Recherches, p. 287.) 
Ritthausen has shown that clover which lies exposed to 
rain after being cut, may lose by washing more than ’|, 
of its ash-ingredients. 
Mulder, (Chemie der Ackerkrume, I, p. 305,) attributes 
to loss by rain a considerable share of the variations in per- 
centage and composition_of the fixed ingredients of plants. 
We must not, however, forget that all the experiments 
which indicate great loss in this way, have been made on 
the cut plant, and their results may not hold good to the 
same extent for uninjured vegetation, which certainly does 
not admit of soaking in water. Further investigations 
must decide this point. 
3. The insoluble matters, or those which become insolu- 
ble in the plant, viz., the sulphate of lime, the oxalates, phos- 
phates, and carbonates of lime and magnesia, the oxides of 
iron and manganese, and silica, may be deposited as crys 
tals or concretions in the cells, or may incrust the cell- 
walls, and thus be set aside from the sphere of vital 
action. 
In the denser and comparatively juiceless tissues, as in 
bark, old wood, and ripe seeds, we find little variation in 
the content of soluble matters. These are present in large 
and variable quantity only in the succulent organs, 
In bark, (cuticle,) wood and seed envelopes, (husks, 
shells, chaff}) we often find silica, the oxides of iron and 
manganese, and carbonate of lime—all insoluble substances 
—accumulated in considerable amount. In bran—the 
vuticle of the kernels of cereals--phosphate of magnesia 
