Natural Sources 



Another ring compound investigated by Schreiner is 

 picoline carboxylic acid (2-methyl-4-carboxy-pyridine). This 

 was originally isolated from a virgin Hawaiian soil by Shorey 

 (1907) and from other soils, and appears to have afforded the 

 first instance of isolation and identification of a definite 

 crystalline organic compound from soil. It was isolated from 

 the virgin Hawaiian soil to the extent of 200 to 300 parts per 

 miUion of soil — a not negligible amount. It was isolated from 

 a Maryland soil by Schreiner and Shorey (1909) by a pro- 

 cedure fully described, though no quantitative details were 

 given. The Maryland soil was "exceedingly" infertile, and 

 Schreiner and Shorey were inclined to ascribe the infertility 

 in part to the presence of the pyridine compound. On testing 

 its eflFect on wheat seedlings, these authors found that in 

 distilled water at a concentration of about one part per million 

 "this soil constituent ... is a stimulant, an effect which is, 

 however, characteristic of small doses of poisons when 

 applied to plants." Uvitonic acid (2-methyl-4: 6-dicarboxy- 

 pyridine) showed no clear evidence of stimulation. It seems 

 possible that a mono-carboxy-pyridine or similar compound 

 may yet be found to have a real "growth-promoting" effect. 

 The Maryland soil did not give notable yield-responses to 

 application of either farmyard manure or artificial fertilizers. 

 Whether this failure to respond was due to sufficiency of ring- 

 compounds, or to excess of a toxic substance such as dihy- 

 droxy-stearic acid, must remain for the present an open 

 question. 



Thornton and Smith (19 14-15) found that growth of 

 the chlorophyll-bearing unicellular animal Euglcena was 

 greatly stimulated by small amounts of phenyl-alanine 



H O 



and tyrosine (hydroxy-phenyl-alanine; \, hydroxy-phenyl- 



acetic acid +NH3), also by hay infusion ; fresh hay infusion, or 

 an infusion that has been long subject to decomposition by 

 microbes, was appreciably less effective towards Euglcena 

 than an infusion subjected for a short time to the action of 

 microbes. Tryptophan was not used in these experiments. 

 Bottomley (191 5-1 7) suggested that the quantity of 



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