ON THE Economic Coefficient of Sugar 469^ 



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the dry weight of the fungus, but more abruptly. For instance, 

 in the case of the cultures with ZnSO, as in the case of irritation 



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it attains its maximum of 0.58 (see general averages, Table V.) at a 

 concentration of 0.004^^ of this salt, at which point also the maxi- 

 mum weight is shown. In solutions of greater strength the co- 

 efficient falls off but more rapidly than does the abnormal growth. 

 At a concentration of 0.03 2/r; when the toxic effect of the ZnSO^ 

 begins to be noticeable the economic coefficient has fallen almost 

 to that of the control as also has the weight of dry substance. 

 In yet stronger solutions in which the growth is much retarded the 

 amount of sugar used remains, however, in about this same rela- 

 tion. The cultures in which Fe.,Cl- was used do not show the 



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same regularity. Up to the strength of o. i^ the rise of the eco- 

 nomic coefficient of the sugar from 0.46 to 0.56 keeps pace with 

 the increase of weight from about 330 mg. to 800 mg. and agrees 

 with the results found with the ZnSO^, but beyond that at a con- 

 centration of 0.2^0 the average of the economic coefficients falls 

 somewhat while the average weight of the fungus crop increases. 

 This was more apparent in the PenicilliuDi cultures than in those 

 with Sterigjnatocystis, In the latter both the weight and ratio re- 

 main about equal, while in the Pcnicilliiun only one series shows 

 any increase (XVIII.) and series XX. indicates a distinct falling off 

 of the coefficient although a considerable gain in weight is shown 



in the 0.2^^ culture over that with buto. i^^ of Fe^Cl^.. It is to be 

 observed, however, that in this case the ratio of 0.82 given for the 

 O. i^j culture stands alone in being the highest found in any series. 

 It is this series that has so materially affected the averages, but 

 since no legitimate reason could be discov^ered for throwing it out 

 it was necessarily included with the rest. In the series with LiCl 

 the two with Stcrigmatocystis show the same peculiarity, for in the 

 stronger concentration of 0.375% there is a distinct gain in weight 

 with some falling off in the availability of the sugar consumed 

 (series XXIL, XXIII.). In the /Iv/zV//////;// cultures the ratio rises 



even in the strongest solution employed but at 0.375^ the gain 

 does not correspond to the increase in weight ov^er the 0,25^ 

 concentration. In the TricJioth:ciuui scries there is no marked 



change. All of the series with LiCl agree, however, in showing 

 in the weaker solutions of o. 125^^0 and 0.25^^ an increase of the 



