( 55 ) 



the t'lingus was ciillivateil on ami in (liileiviil iiiilri(i\o nialerials of 

 known composition. 



Tt apjieared in tlie first ])laco that tlie presence of free oxyjien is 

 ahsohitely neoessai-y foi- its growth; witli anaerobic nietiiods of cui- 

 tivation according lo IUchner and LiBomrs no li-ace of development 

 look phice. Il is not iinprohabU' lliat this is the reason \\\\\ the 

 nncelinni only grows extremely slowly in nntrient licpiids, ^vll(M•e I he 

 (piantity of oxygen below the snrface is necessarily small. 



On the other iiand the fnngns appeared to grow very ra|):dlv 

 when inocnlated on malt-gelatine, malt-agar and also on parts of 

 leaves and stems of the tobaccoplant, sterilised at a high temperature. 

 Then a woolly mycelium developed, in some [)laces rising above the 

 snrface. Helow the snrtace of liquids or filtrates, obtained from parts 

 of stems or leaves, after inoculation with the finigus, oidy a meagre 

 cloudy mycelium ai)peared. As soon however as part of this had 

 reached the snrface of the liquid, its growth became nuu'h more 

 vigorous. In some cases a floatiiig sclerotiuni was e\'en produced. 



Next the influence of the reaction of the nntrient liquid was studied. 

 In a solution of O.iVo ^^ potassium nitrate, 0.57„ glucose, ().0507o 

 magnesiumsulphate and 0.050" /„ potassiununono|)liosphate, containing 

 carbon and nitrogen assimilable by the fungus, Sderotln'ui Nlcotiuiae 

 does not easily su[)[)ort free acid or alkali. The acid limit lies \\\\\\ 

 this solution at about J cubic centimetre of Vm normal sulphuric 

 acid to 100 cubic centimetres of liquid, and the alkaline limit at 

 0.5 cM' of Vio normal potassiumhydrate. Neither limit can be sharply 

 drawn as the fungus only slowly produces acid in the solution men- 

 tioned. With 1.5 cM'. of \/i„ normal sulphuric acid no growth 

 whatever takes place any longer; with tlie alkaline solution tlie 

 limit could not be sharply defined. 



Moreover an elaborate investigation was made as to which com- 

 pounds were profitable to the fungus as carbonaceous and \\liich as 

 nitrogenous foods. As a carbonaceous food glycose, as a nitrogenous 

 one saltpetre in the al)o\'e-mentioned concentration, proved most 

 satisfactory. Ammonium nitrate, a very good nitrogenous food, was 

 not available of course in the presence of alkalies. 



In the further experiments the saltpetre was replaced by a similar 

 quantity M).l 7o) of ^^^c nitrogen comj)Ouiul to be studied or the 

 glycose by the carbon compound to be studied in the same con- 

 centration. 



a. Nitrogenous food. 



Nitrogen was offei-ed to the fungus in the form of ]>otassium 



