ORGANIC MATTERS OF THE SOIL. 233 
weight of the humus decreased 9 milligrams, The 
Polygonum during 10 days gained 3,5 gims., and the 
solution lost 48 milligrams of humus. These experi- 
ments Liebig considers undecisive, because an alkali- 
humate loses weight by oxidation (to carbonic acid and 
water) when exposed in solution to the air. Mulder, how- 
ever, denies that any appreciable loss could occur in such 
a solution during the time of experiment, and considers 
the trials conclusive. 
In a third experiment, De Saussure placed the roots of 
Polygonum Persicaria in the water-extract of turf con- 
taining no humic acid but crenic and apocrenic acids, 
where they remained nine days in a very flourishing state, 
putting forth new roots of a healthy white color. An 
equal quantity of the same extract was placed in a simi- 
lar vessel for purposes of comparison. It was found that 
the solution in which the plants were stationed became 
paler in color and remained perfectly clear, while the other 
solution retained its original dark tint and became turbid. 
The former left after evaporation 33 mgrms., the latter 39 
mgrms. of solid residue. The difference of 6 mgrms., De 
Saussure believes to have been absorbed by the plant. 
Wiegmann and Polstorf (Ueber die unorganischen Be- 
standtheile der Pflanzen) experimented in a similar man- 
ner with Mentha undulata, a kind of mint, and Polygonum 
Persicaria, using two plants of 8 inches height, whose 
roots were well developed and perfectly healthy. The 
plants grew for 30 days in a wine-yellow water-extract 
of leaf compost (containing 148 mgrms. of solid sub- 
stance—organic matter, carbonate of lime, etc.,—in 100 
grams of extract), the roots being shielded from light, 
and during the same time an equal quantity of the same 
solution stood near by in a vessel of the same dimensions. 
The plants grew well, increasing 6} inches in length, and 
put forth long roots of a healthy white color. On the 
18th of July the plants were removed from the solution, 
