204 HOW CROPS GROW. 



Saussure proved that foliage readily yields up saline 

 matters to water. He placed hazel leaves eight success- 

 ive times in renewed portions of pure water, leaving them 

 therein 15 minutes each time, and found that by this 

 treatment they lost ^ of their ash-ingredients. The 

 portion 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 one- 

 half of its ash-ingredients. 



Mulder (Chemie der AcTcerlcrume, II, p. 305) attributes 

 to loss by rain a considerable share of the variations in 

 percentage and composition of the fixed ingredients of 

 plants. We must not, however, forget that all the exper- 

 iments 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. 



3. The insoluble matters, or those which become so in 

 the plant, viz., the calcium sulphate, the oxalates, phos- 

 phates, and carbonates of calcium and magnesium, the 

 oxides of iron and manganese, and silica, may be depos- 

 ited as crystals 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 amount 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 calcium carbonate all insoluble 

 substances accumulated in considerable amount. In 

 bran, phosphate of magnesium exists in comparatively 

 large quantity. In the dense teak wood, concretions of 

 calcium phosphate have been noticed. Of a certain 



