194 HOW CROPS GROW. 



11.2% of oxide of manganese in ash of leaves of the red 

 beech (Fagus sylvaticd) that contained but 1% of oxide 

 of iron. In the ash of oak leaves (Quercus robur) Xeu- 

 bauer found, of the former 6.6, of the latter but 1.2%. 



In ash of the wood of the larch (Larix Europcea), Bot- 

 tinger found 33.5% Mn 3 4 and 4.2% Fe 2 3 , and in ash 

 of wood of Pinus sylvestris 18.2% Mu 3 4 , and 3.5% 

 Fe 2 3 . In ash of the seed of colza, Nitzsch found 16.1% 

 Mn 3 4 , and 5.5 Fe 2 3 . In case of land plants, these 

 high percentages are accidental, and specimens of most 

 of the plants just named have been analyzed, which were 

 free from all but traces of oxide of manganese. 



Salm-Horstmar concluded from his experiments that 

 oxide of manganese is indispensable to vegetation. 

 Sachs, Knop, and most other experimenters in water- 

 culture, make no mention of this substance in the mix- 

 tures, which in their hands have served for the more or 

 less perfect development of a variety of agricultural 

 plants. Birner & Lucanus have demonstrated that man- 

 ganese is not needful to the oat-plant, and cannot take 

 the place of iron. ( Vs. St., VIII, p. 43.) 



Is Chlorine Indispensable to Crops ? What has 

 been written of the occurrence of sodium in plants ap- 

 pears to apply in most respects equally well to chlorine. 

 In nature, sodium is generally associated with chlorine 

 as common salt. It is most probably in this form that 

 the two substances usually enter the plant, and in the 

 majority of cases, when one of them is present in large 

 quantity, the other exists in corresponding quantity. 

 Less commonly, the chlorine of plants is in combination 

 with potassium exclusively. 



Chlorine is doubtless never absent from the perfect 

 agricultural plant, as produced under natural conditions, 

 though its quantity is liable to great variation, and is 

 often very small so small as to be overlooked, except by 

 the careful analyst. In many analyses of grain, chlorine 



