180 HOW CBOPS GEOW. 



ash of -wood of Finns sylvestris 18.2° |„ Mn^ 0„ and 3.5° |, 

 Fe, O3. In ash of the seed of colza, Mtzsch found 16.1° |„ 

 Mttj 0„ and 5.5 Fe^ O3. In case of land plants, these high 

 percentages are accidental, and specimens of most of the 

 plants just named hare heen analyzed, which were free 

 from all but traces of oxide of manganese. 



Salm-Horstmar concluded from his experiments that 

 oxide of manganese is indispensahle to vegetation. Sachs, 

 Knop, and most other experimenters in water-culture, make 

 no mention of this substance in the mixtures, which in 

 their hands have served for the more or less perfect devel- 

 opment of a variety of agricultural plants. Birner & • 

 Lucanus have demonstrated that manganese is not needful 

 to the oat-plant, and cannot take the place of iron. ( Ys. 

 St., Yin, p. 43.) 



Is Chlorine indispensable to Crops? — TVTiat has 



been -written of the occurrence of soda in plants ap- 

 pears to apply in most respects equally well to chlo- 

 rine. In nature, soda, or rather sodium, is generally 

 associated with chlorine as common salt. It is most prob- 

 ably 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 correspond- 

 ing quantity. Less commonly, the chlorine of plants is in 

 combination with potassium exclusively. 



Chlorine is doubtless never absent from the perfect agri- 

 cultural 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 is not men- 

 tioned. Its absence, in many cases, is due, without doubt, 

 to the fact that chlorine is readily dissipated from the ash 

 of substances rich in phosphoric, silicic, or sulphuric acids, 

 on prolonged exposure to a high temperature. In the 

 later analyses, in which the vegetable substance, instead 

 of being at once burned to ashes, at a high red heat, is 



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