874 



SCIENCE. 



[N. S. Vol. XXV. No. 648 



when the last crop of wheat was removed on 

 December 8. 



An interesting case is that of the two pine 

 seedlings. During the growth of the first crop 

 one of these died, and the pot with the dead 

 seedling left intact was carried on in the set 

 and treated in the same way as the other 

 eidtures. The greater yield in this pot over 

 that in the pot containing the live pine is 

 clearly evident. 



Another feature is the variation in yield ob- 

 tained in the pots with different species of 

 trees. It would appear that the cherry was 

 least active in checking growth of wheat, the 

 dogwood next, followed by the tulip, then 

 maple, and most of all, live pine, although it 

 would not be safe to assume this same order 

 would obtain in the field. 



It should be mentioned that in replanting 

 the wheat, the soil was disturbed only enough 

 to accomplish this, so the organic matter left 

 by the wheat roots would act as a light appli- 

 cation of green manure, although it is well 

 known that wheat is not very effective as green 

 manure. This would perhaps help slightly to 

 counteract the deleterious effect of the tree 

 roots on the wheat, but the aim was to leave 

 the soil undisturbed. 



Summarizing the foregoing, we find that 

 seedling trees of tulip, dogwood, maple, cherry, 

 and pine retard growth of wheat when the 

 latter is grown under conditions making it 

 necessary for the wheat roots to be in close 

 physical relation with the tree roots. That 

 this retarding effect differs with different 

 species of tree seedlings, that the checking of 

 wheat growth is greatest during the season 

 when the tree seedlings are most active physi- 

 ologically, and this checking effect becomes 

 less as the season of physiological inactivity 

 of the trees is approached. That in the case 

 of pine, at least, the live pine is much more 

 detrimental to wheat growth than the dead 

 pine. 



This injurious effect of trees on wheat ap- 

 pears to be due to the excretion of substances 

 by the trees, toxic to wheat growth. 



Charles A. Jensen 



BtiEEAu OF Soils, 

 U. 8. Depaetment op Agkictiltuee, 

 Washington. D. C. 



yOrE'S ON ORGANIC CHEMISTBY 

 FORMATION OF FUSEL OIL 



The production of fusel oil during the 

 course of the ordinary alcoholic fermentation 

 involves grave practical difficulties to the 

 manufacturer of distilled spirituous beverages, 

 because the removal of this constituent entails 

 a considerable expense. To the pure chemist 

 also, this formation of fusel oil is of im- 

 portance because it, apparently, complicates 

 the chemical changes involved in the course of 

 fermentation. The conversion of grape sugar, 

 CjHijOe, into alcohol, SC^H.O, and carbon 

 dioxide, 200^, is very simple, but to account 

 for the production of small, variable amounts 

 of amyl alcohol and similar substances com- 

 pels the use of quite complicated equations. 

 The difficulties of both the brewer and the 

 chemist wiU be lessened, or wholly removed 

 by some highly interesting work which Felix 

 Ehrlich'^ has carried out in the Berlin Institu- 

 tion of Sugar Industry. He has fermented 

 pure sugar solutions with pure yeast cultures 

 and obtained, on an average, about 0.4 per 

 cent, of fusel oil. The addition of Z-leucine, 



^5^ > CHCHjCH ( NHj ) COjH, 



or of di-isoleucine, 



^^3>CHCH (NHj) COjH, 



to the fermenting material immediately raised 

 the content of fusel oil to 3 per cent. The 

 former compound gave inactive amyl alcohol, 



^gs>CHCHjCHsOH, 



and the latter, optically active, dextro-rotatory 

 amyl alcohol, 



^?3 >CHCH,OH. 



On comparing the formulae it will be observed 

 that the alcohols can be formed from the 

 leucines by the addition of the elements of 

 water and the elimination of ammonia and 

 carbon dioxide. 



The latter substance is, of course, evolved, 

 and the question arises as to the fate of the 

 ammonia. Special experiments showed that 

 the fermenting liquid and the gases issuing 

 from it were free from ammonia and nitrogen, 



'Ber. d. chem. Ges., 40, 1027 (1907). 



