Inorganic Constituents of Plants. 505 



a method of quantitative ash-analysis, the ashes of vegetables 

 can be generally classed according to the prevalence of some 

 of their constituents. 



All vegetable ashes can be arranged according to their 

 composition in the three following groups : — 



(a.) Ashes rich in Alkaline and earthy Carbonates. — To this 

 group belong the ashes of woods, herbaceous plants and li- 

 chens, inasmuch as these abound in salts of organic acids. 



(b.) Ashes rich in Alkaline and earthy Phosphates. — Almost 

 all seeds yi^ld ashes belonging to this division. 



(c.) Acids rich in Silica, — The stems of the Grasses, the 

 Equisetaceae, &c., yield ashes of this kind. 



It will be seen that this classification cannot be strict, and 

 that besides the instances already known, many others will 

 occur of members of the different classes assimilating. The 

 ashes of the mistletoe {Fisctun album), for example, form a 

 link between the first and second groups, inasmuch as they 

 contain considerable quantities both of carbonates and of phos- 

 phates ; the same may be said of those of the seeds of the oak 

 (Quet'cus robur) and of the chestnut [Fagus castaned). Again, 

 the ashes of some seeds, as millet [Millium sativum), oats 

 {Ax)ena sativa), barley [Hordeum vulgare), contain so much 

 silica that they might with equal propriety be placed in the 

 third as in the second group. 



The division of plants into potash, lime and silica plants is 

 quite inadmissible, since it would be inconsistent with the 

 beautiful law of substitution established by Professor Liebig. 

 According to this law, the predominance of the one or the 

 other of the above-named bases in the ashes of a plant depends 

 upon the quantities of each existing in the soil. Tobacco 

 would generally be considered as belonging to the lime group ; 

 the result of recent analyses, of great interest in reference to 

 the law mentioned above, prove however that tobacco would 

 equally belong to the potash group if grown upon a soil in 

 which that base abounded. 



We now proceed to describe a method of quantitative ash- 

 analysis which, as yet, we have found to be the simplest, and 

 therefore most to be depended upon. The details of the 

 process comprise but little that is new to science, whilst a me- 

 thod, more or less similar, might easily have been arranged 

 by any experienced chemist. We are nevertheless of opinion 

 that circumstances justify its ample consideration. The sub- 

 ject is as yet but partially investigated, and there are doubtless 

 chemists appreciating its importance, and desirous of enter- 

 ing upon the inquiry, to whom it will be a desideratum to be 

 possessed of a method, into the correctness of which they need 

 not themselves laboriously examine. 



Phil. Mag. S. 3. No. 169. Suppl. Vol. 25. 2 L 



