THE ASH OF PLANTS. 179 



potato tuber. The proportion of ash is, however, so small 

 that in case of potato-albumin, the oxide of iron amounts 

 to but 0.12 per cent of the dry substance. (Der Rationelle 

 AcJcerbau, p. 82.) 



In the wood, and especially in the bark of trees, oxide 

 of iron often exists to the extent of 5-10 | . The largest 

 percentages have been found in aquatic plants. In the ash 

 of the duck-meat, (Lemna trisulca,) Liebig found 7.4 | . 

 Gorup-Besanez found in the ash of the leaves of the Trapa 

 natans 29.6 | , and in the ash of the fruit-envelope of the 

 same plant 68.6| . (Ann. Ch. Ph., 118. p. 223.) 



Probably much of the iron of agricultural and land 

 plants is accidental. In case of the Trapa natans, we 

 cannot suppose all the oxide of iron to be essential, be- 

 cause the larger share of it exists in the tissues as a brown 

 powder, which may be extracted by acids, and has the ap- 

 pearance of having accumulated there mechanically. 



Doubtless a portion of the oxide of iron encountered in 

 analyses of agricultural vegetation has never once existed 

 within the vegetable tissues, but comes from the soil which 

 adheres with great tenacity to all parts of plants. 



Oxide of Manganese, Mn, 4 , is unessential to Agri- 

 cultural Plants. This oxide is commonly less abundant 

 than oxide of iron, and is often, if not usually, as good as 

 wanting in agricultural plants. It generally accom'panies 

 oxide of iron where the latter occurs in considerable quan- 

 tity. Thus, in the ash of Trapa, it was found to the extent 

 of 7.5-14.7| . Sometimes it is found in much larger quan- 

 tity than oxide of iron; e. g., C. Fresenius found 11.2 | 

 of oxide of manganese in ash of leaves of the red beech, 

 (Fagus sylvatica,) that contained but 1| of oxide of iron. 

 In the ash of oak leaves, ( Quercus robur,) Xeubauer found, 

 of the former 6.6, of the latter but 1.2 | . 



In ash of the wood of the larch, (Larix, JSuropceaj) 

 Bottingcr found 13.5 | Mn a O 4 and 4.2J Fe 2 O 3 , and in 



