ON THE Economic Coefficient of Sugar 465 



were selected. The sowings of the fungus spores were not made 



X I 



by the addition of water in which the spores hung suspended, 

 since it was desired not to weaken the solutions and thereby in- 

 volve another chance of error in the subsequent analyses. Instead 

 of this method, small pieces of heavy glass rod (about 8 mm. 

 diam.) were taken, their ends slightly moistened and then rubbed 

 on the dry stock culture of the desired fungus. The bits of glass 

 rod, with the attached spores, were then dropped in the prepared 

 flasks ; a slight shaking served to dislodge the spores which 

 promptly rose to the surface and with sufficiently even distribution 

 to insure an ev^n growth of the fungus when they germinated. 

 In this way the cultures were provided with at least an approxi- 

 mately equal number of spores, certainly above the maximum re- 

 quired to produce an unbroken carpet of mycelium, and that, as 



■ 



has already been shown, is sufficient to make an equal growth on 

 surfaces of the same area, \ 



¥ I 



r ■ 



As in the previous investigations the greatest care was taken 

 to have all of the substances used for the culture fluids of the 

 greatest practicable degree of purity. The chemically pure salts 



I 



prepared by Merck & Co. were used and again reciystallized. 

 The sugar was of the best quality obtainable in the market and 



I 



showed on many tests to be free from impurities. The water 

 was twice distilled, once over a tin-lined still and the second time 



I 



over glass with alkaline permanganate. It should be added that 

 due care was taken that none of the permanganate passed over. 

 By all tests employed as well as by the evidence of the experi- 

 ments themselves, the water was shown to be pure.' For the irri- 



I 



tant substances, the zinc sulphate and lithium carbonate, from which 

 the chloride was prepared, were kindly given the writer by Profes- 

 sor T. W. Richards, of Harvard University. Of the other salts 

 the nickel sulphate and the ferric chloride were the purest obtain- 

 able and further purified by successive recrystallizations. 



Only one nutrient solution was used — that recommended by 

 Pfeffer ^ which is identical with solution A of the writer's previous 

 paper. t The formula is as follows : 



^ p]lcction organischcr NahrstofTe. Prings. Jahrb.,. 27 : 23S. 1895. PHanzen- 

 physiologic, i : 375. 



■)■ Richards, /. c. p. 667. , 



