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 J | 15 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 a | 3 

 of its ash-ingredients. 



Mulder, ( Chemie der AcJcerJcrume, II, 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 

 cuticle of the kernels of cereals phosphate of magnesia 



