15 



plants, to protect them from falling when the soil is wet or 

 from being blown down by heavy winds. One or two hoe- 

 ings are necessary during the growing period to keep down 

 the weeds, as everything that detracts from the growth of 

 the plant is detrimental to the ([uality of the leaf. 



VII. Chemical Properties. 



An analysis of the ashes of tobacco by I'rofessor .Johnson 

 shows the following constituents in their several propor- 

 tions (per cent.) : 



Potash 12.14 



Soda 0.07 



Lime 45 • 90 



Magnesia 13-^9 



Chloride of Sodium 3 .49 



Chloride of Potassium 3-98 



Phosphate of Iron 5-48 



Phosphate of Lime i • 49 



Sulphate of Lime 6.35 



Silica 8.01 



100.00 

 From tliis analysis it will be observed that of the min- 

 eral matters contained in tobacco, the following predomi- 

 .nate: silica, potash, lime and magnesia, with a large pro- 

 iportion of the phosphate of iron and sulphate of lime. 



There is in tobacco a volatile akali which may be known 

 hy its smoke changing the color of flowers — turning red 

 to purple and purple to green. Different kinds of tobacco 

 are distinguished by the peculiar odor emitted. This va- 

 riation is in part due to the different modes of curing the 

 leaf. 



Recent Tiivestigations;. — Many new investigations have 

 ,been made as regards the tobacco crop, referred to under 

 the foUowino: heads.* 



■ft 



=^Dr. J. Nessler, of Karlsruhe (Landw. vers. Stat. 40, pp. 395-438) Ex- 

 periment Station Record, October, 1SH2. 



