THE ASH OF PLANTS. 195 
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 acid, would have 
made 13.7°|, of the fixed ingredients, or one per cent of 
the dry leaf itself* 
Other ash-ingredients.—Salm-Horstmar has described 
some experiments, from which he infers that a@ minute 
amount of Lithia 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 Titanic 
acid is a necessary ingredient of plants. The later results 
‘of water-culture would appear to demonstrate that these 
conclusions are erroneous. 
It is, however, possible, as Mulder has suggested, ( Ohe- 
mie der Ackerkrume, II, 341,) that the failure of certain 
crops, after long-continued cultivation in the same soil, 
may be due to the exhaustion of some of these less abun- 
dant and usually overlooked substances. Land not unfre- 
quently becomes “clover-sick,” 7. ¢., refuses to produce 
good crops of clover, even with the most copious manur- 
ings. In Vaucluse, according to Mulder, the madder crop 
has suffered a deterioration in quality—the coloring effect 
of the root having diminished one-fourth—as an apparent 
result of long cultivation on the same soil, although the 
seed is annually renewed from Asia Minor, and great care 
is bestowed on its culture. 
The newly discovered element, Rubidium, has been 
found ‘in the sugar-beet, in tobacco, coffee, tea, and the 
* Arendt was the first to estimate sulphuric acid in vegetable matters with 
accuracy, and to discriminate it from the sulphur in organic compounds. This 
chemist determined the sulphuric acid of the oat-plant by extracting the pulver- 
ized material with acidulated water. He likewise estimated the total sulphur by 
a special method, and by subtracting the sulphur of the sulphuric acid from the 
total, he obtained as a difference that portion of sulphur which belonged to the 
albuminoids, etc. In his analyses of clover, Ulbricht followed « similar plan. 
(Ve. St., WI, p. 147.) As has already been stated, many of the older analyses 
are wholly untrustworthy as regards sulphur and sulphuric acid. 
