5. Entwicklungslehre. 729 



junge Gerstchenpflänzchen festzustellen mit besonderer Rücksicht darauf, in 

 welchen Konzentrationen diese Salze stimulierend und toxisch wirken. Die 

 Schlußfolgerungen ans den Kulturbeobachtungen sind: Die Wirkung von Pflanzen- 

 giften in flüssigen Lösungen wird durch die Gegenwart von Nährsalzen verdeckt; 

 in Wasserkulturen ertragen bei Gegenwart von Nährsalzen die Pflanzen viel höhere 

 Konzentrationen der Giftstoffe als ohne sie. Kupfersulfat hat keinen stimu- 

 lierenden Einfluß auf die Gerste, für die es ein typisches Gift ist, selbst bei 

 niedrigen Konzentrationen von 1 auf 10 Millionen. Mangansulfat ist kein so 

 entschiedenes Gift, aber es verzögert das Wachstum sehr bedeutend, wenn es 

 in mäßiger Quantität vorhanden ist. Kleine Spuren davon üben eine stimu- 

 lierende Wirkung auf Wurzel und Stengel aus. Wenn Mangansulfat in ge- 

 nügender Konzentration vorhanden ist, so wird es von der Pflanze aufgenommen 

 und in den unteren Blättern abgelagert. Lindau (Berlin). 



1583) Schreiner, 0. and J. J. Skinner (Bur. Soils, Dept. Agr. Washington), 



Some Effects of a Harmful Organic Soil Constitueut. 

 (U. S. Dept. Agr. Bur. Soils, Bulletin 70. p. 1—98. 1910.) 



This paper gives an aecount of the results of an extensive series of ex- 

 periments on the effect of an organic Compound, dihydroxystearic aeid, which 

 may be isolated from unproduetive soils, on the growth in eulture Solutions 

 Of seedling wheat plants. This Compound may be prepared in the laboratory 

 by ,starting with oleic aeid, which by treatment with nitrous oxide is changed 

 to the isomeric elaidic aeid. The elaidic aeid thus formed is dissolved in a 

 Solution of potassium hydroxide and oxidized by a Solution of potassium per- 

 manganate, one of the produets under suitable conditions be ng dihydroxystearic 

 aeid. Care has to bc taken that the oxidation does not proeeed too far, for 

 the dihydroxystearic aeid very readily oxidized to other Compounds*. 



The chief results of this careful and detailed study, which are of in- 

 terest not only from the Standpoint of soil chemistry but also, and even more 

 so, from the Standpoint of plant physiology are as follows: Dihydroxystearic 

 aeid hinders the growth of wheat plants when this is present in Solution in 

 pure distilled water. The Compound is also harmful in the presence of nu- 

 trient or fertilizer salts in all ratios of the fertilizer elements, P2O-, NH 3 , 

 and K.,0. Tlic Compound is more harmful in those ratio of fertilizer elements 

 not well snited for plant growth. The harmful effect of the Compound is the 

 least in those ratios of fertilizer elements best snited for plant growth. The 

 Compound appears to be relatively mach less harmfnl in the presence of ferti- 

 lizers mainly nitrogenous than in the pre ence of fertilizers mainly phosphatic 

 or potassic. The harmful Compound modified greatly the removal fertilizer 

 elements from the Solutions. The quantity of phosphate and potash removed 

 paa less in the presense of the Compound, bat the nitrate was not so in- 

 fluenced and 011 the winde the amount removed was even greater. The eom- 

 ponnd modified botli amonnl and ratio of the three fertilizer elements removed 

 from Solutions, the ratio being higher in uitrogen, which was also the most 

 efficient fertilizer dement in decreasing the harmful effect, as above men- 

 tioned-. 



,The harmfnl Compound has the additional effect of darkening the root 

 ups, stunting root development, causing enlarged root ends, which are often 

 ; upward like fishhooks, and inhibiling Btrongly the oxidizing power of 

 the roots. Those fertilizer combinations which tend to increase root oxidation 

 are also the combinations which overcome the harmfnl effects to the greatest 

 extent. Incidentally the investigat on* also throw mach lighl upon the relations 

 between plant growth and fertilizer action. The bester growth oecurred 



43* 



