ORGANIC mattkus of TIIK SOIt. S33 



weight of tlie humus decreased 9 rnilligrams. The 

 Polygonum during 10 days gained 3,5 gims., and the 

 solution lost 43 milligrams of humus. These experi- 

 ments Liebig considers undecisive, because an alkali- 

 humate loses weight by oxidation (to carbonic acid and 

 Avater) 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, 

 jDUtting 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 ( Ueher die unorganisclien Be^ 

 standthe'de der Pflanzen) experimented in a similar man- 

 ner with Mentha und^data^ 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 Q>\ 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, 



