136 THE ROLE OF NITROGEN IN PLANT MIOTABOLISM, V., 



130 gms. of crystals which, on dissolving in water and re- 

 crystallising, formed two layers. The surface-layer con- 

 sisted of lath-shaped crystals of potassium nitrate, about 1 

 inch long ; and the second, a considerable quantity of small 

 cubical crystals of potassium chloride. These potassium salts 

 were obtained as a by-product only ; and the superfluid pos- 

 sessed the odour of strong tobacco, but only a very small 

 amount of alkaloid was obtained from it. 



Result .— In the solution of crystals, the nitrate was deter- 

 mined by the nitrometer, and gave 58 gms. of potassium 

 nitrate. The volume of the combined mother-liquors, from 

 which the crystals had been obtained, was 1300 cc, and, 

 taking this as a saturated solution, it contained 292 gms. 

 The total amount is, therefore, 350 gms. potassium nitrate, 

 equivalent to 2-01% of the plant dried at 110° C. A sample 

 of the plant dried at 110", contained 16/ of inorganic matter. 



The experiments of Andre* show that the amount of nitrate 

 in plants generally varies with the period of life. It in- 

 creases to a maximum with the formation of flower-buds, and 

 rapidly diminishes again to a small amount. From this we 

 see that the SoJandra leaves were collected at a time when 

 their nitrate-content would be a minimum. 



Historical. — As long ago as 1747, Stahlf noticed the exis- 

 tence of nitre in the tobacco plant ; and Braconnoti, in 1827, 

 records the abundance of this salt in certain plants ; its wide 

 distribution in the phanei'ogams was also shown by De 

 Candolle§. In the following plants, nitrates occur as 

 reserve-material stored in exceptionally large amounts, which 

 are expressed as potassium nitrate of the whole plant or 

 part, dried at 100° C. 



* f-.R. 142, 1900, 106. 

 t Stahl. — FuiiHamenta Chymirp, 1747, p. 105. 

 :J: Braconnot. — Annal. chim. physiq. (2), 35, 1827, p.260. 

 § De Candolle. — Physiologie, i., 383. 



