IN THE VEGETABLE KINGDOM. 191 



Potash .... .... 14'1 ; in which there were 2*4 parts oxygen. 



Soda 20-7; 5'3 



Lime 13'6; 3'82 



Magnesia 43'5 ; T69 



Sum of the bases 5275; Sum of the oxygen 13-21 



We must abstract from the oxygen of the bases in the first 

 analysis 0*53 parts, and from that of the second analysis 0'79 parts, 

 which belong to the bases which are combined with sulphuric and 

 phosphoric acids ; so that there would be 12*66 parts of oxygen for 

 the first, and 12 '42 for the second determination of oxygen. 



The idea that these equal quantities of oxygen indicate that 

 there are equal quantities of acid to be saturated in the fresh plant, 

 seems so obvious that its correctness might have been a priori 

 suspected. At the same time, it was to be expected that 

 this proposition would, under varying circumstances, be open to 

 nnmerous exceptions, and that the direct results of the ash-analyses 

 would rarely so accurately coincide as in the instances we have 

 recorded. It is not, however, solely on account of their basic 

 character that these alkalies and earths are necessary for certain 

 plants ; for we know, for instance, that in very many plants the 

 potash at all events cannot be thoroughly replaced by soda ; thus, 

 for example, scarcely a trace of soda can be found in the ash of the 

 horse-chesnut, even when the tree has grown in a soil in which 

 this alkali abounds (E. Wolff, Staffel). The salts of soda are 

 indeed absorbed in such cases, like other substances which are 

 unsuited to the nutriment of the plant, but they are then speedily 

 excreted, and principally by the roots. 



We find in the ash of many plants, amongst others in that of 

 the Cacti, that there is a much larger amount of carbonate of lime, 

 and therefore a higher number for the oxygen of the bases, than 

 corresponds to the true nutrient process of the plants. The car- 

 bonate of lime is here in part produced from the oxalate of lime, 

 which is frequently deposited in the cells in a crystalline form, 

 either as dead matter or as an excretion. Carbonate of lime is 

 also deposited in a similar manner in many plants. 



An exception to this rule, which may, however, be regarded as 

 a proof of the correctness of the main proposition, is furnished by 

 Liebig's discovery of the frequent occurrence of vegetable bases 

 under relations in which the plant could not be supplied with any 

 abundant amount of mineral constituents. Liebig draws attention 

 to the fact that the quantities of the alkaloids found in cinchona 



