THE ASH OF PLANTS. 209 



of the fixed ingredients. In the clover leaf, at a time 

 when it was totally destitute of sulphates, there existed 

 an amount of sulphur which, in the form of sulphuric 

 oxide, would have made 13.7% of the fixed ingredients, 

 or one per cent of the dry leaf itself.* 



Other ash-ingredients. Salm-Horstmar has describ- 

 ed some experiments, from which he infers that a minute 

 amount of Lithium and Fluorine (the latter as fluoride 

 of potassium) are indispensable to the fruiting of barley. 

 (Jour, fur prakt. Chem., 84. p. 140.) The same observer, 

 some years ago, was led to conclude that a trace of Titan- 

 ium is a necessary ingredient of plants. The later re- 

 sults of water-culture would appear to demonstrate that 

 these conclusions are erroneous. 



The rare alkali-metal, Rubidium, has been found in the 

 sugar-beet, in tobacco, coffee, tea, and the grape. It doubt- 

 less occurs, perhaps together with the similar Caesium in 

 many other plants, though always in very minute quan- 

 tity. Birner and Lucanus found that these bodies, in the 

 absence of potassium, acted as poisons to the oat. ( Vs. 

 St., VIII, p. 147.) 



According to Nobbe, Schroeder and Erdmann, Lith- 

 ium is very injurious to buckwheat, even in presence of 

 potassium. When lithium was substituted for two- 

 thirds of the potassium of a normal nutritive solution, 

 buckwheat vegetated indeed for 3 months, the stem 

 reaching a length of 18 inches, but the plant was small 

 and unhealthy, the leaves were pale and the older ones 

 dropped away, as shown by VIII, plate I. (Vs. St., 

 XIII, p. 356). 



*Arendtvrns the first to estimate sulphuric oxide (SO 3 ) in vegetable 

 matters with accuracy, and to discriminate it from the sulphur of or- 

 ganic compounds. This chemist separated the sulphates of the oat- 

 plant by extracting the pulverized material with acidulated water. He 

 likewise estimated the total sulphur by a special method, and by sub- 

 tracting the sulphur of the sulphuric oxide from the total he obtained as 

 a difference that portion of sulphur which belonged to the albuminoids, 

 etc. In his analysis of clover, t'/hrifltt followed a similar plan. ( f r s. St., 

 Ill, p. 147.) As has already been stated, many of the older analyses are 

 Wholly untrustworthy as regards sulphur anil sulphuric oxide. 



