THE ASH OF PLANTS. 203 



Similar results were obtained by Councler with the 

 leaves of Acer negundo (Vs. St., XXIX, p. 242), 1,000 

 parts of the perfectly dry leaves contained : 



Water-plant. Soil-plant. 



Silica, SiO 2 , 8.51 23.72 



Sulphuric oxide, SO 3 , 38.97 9.69 



Phosphoric oxide, P 2 O 6) ... 26.00 4.56 



Iron oxide, Fe 2 O s , 1.94 1.22 



Magnesium oxide, MgO,. .. 7.56 6.25 



Calcium oxide, CaO 31.77 36.17 



Sodium oxide, Na 2 O, 1.23 0.88 



Potassium oxide, K,O, 96.92 45.05 



212.90 127.54 



Leaves of the water-plant are much richer in ash-ingre- 

 dients, especially in sulphate and phosphate of potassium. 

 Those of the soil-plant contain more silica and lime. 



Disposition by the Plant of Excessive or Super- 

 fluous 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 themselves, and also incapable of forming in- 

 soluble combinations with other ingredients of the plant 

 viz., the alkali chlorides, sulphates, carbonates, and 

 phosphates, the chlorides of calcium and magnesium, 

 may 



1. Eemain 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. (Vs. St., VI, p. 37.) 



Saussure found in the white incrustations upon cucum- 

 ber leaves, besides an organic body insoluble in water and 

 alcohol, calcium chloride with a trace of magnesium 

 chloride. The organic substance so enveloped the cal- 

 cium chloride as to prevent deliquescence of the latter. 

 (Recherches sur la Veg., p. 265.) 



