

2 Curtis : Turgidity in Mycelia 



could easily be detected, it was possible to test the turgor force at 

 the instant of the recovery from the effect of the change of sub- 



stratum. The basis 



periments 



% 



sugar, . 5 % peptone and . 5 % beef extract, and from this were 

 made solutions containing various gram-molecule percentages of 

 potassium nitrate. By this means the plants were always afforded 

 a constant nourishment and the effects of the introduction of a 

 known factor, potassium nitrate, could readily be determined. In 

 many respects the hyphae of the lower fungi are especially 

 adapted to this character of work since they are easily cultivated 



mar 



velous degree, adaptability to varying degrees of concentration 

 without injurious results, and are so simple in structure that 

 changes of culture media produce immediate reactions. Many 

 will grow in a saturated potassium nitrate solution, about 23%, 

 and some will endure a transfer from relatively strong to zero so- 

 lutions without bursting. The suitableness of these plants for 

 measuring the turgor force is more apparent when we consider that 

 Pfeffer has determined that in an artificial cell a 1% potassium 

 nitrate solution produced a pressure 175.8 cm. of mercury, and 

 that this estimate is low since the precipitation membrane is some- 

 what permeable for potassium nitrate. 



It was found impossible to study the behavior of the mycelia 

 in gelatine or agar since these media not only dissolve at relatively 

 low concentrations of the substratum, but they are also objection- 

 able as being somewhat unstable and permitting a rather slow and 

 gradual penetration of the various culture solutions. Gypsum 

 proved a fairly satisfactory means of fixing the spores for germi- 

 nation and subsequent study. The powdered gypsum was mixed 

 into a paste with water, and to this mass the spores were added. The 

 mass was then readily pressed out into a thin plate between glass 

 slides, and hardens in a few minutes. These thin plates, however, 

 were somewhat difficult to fasten to the slides, and are liable to break 

 during an experiment. So attempts were made to germinate the 

 spores in floss silk and strands of cotton fibers fastened to the 

 cover glass with drops of balsam, and this led to a very simple 

 and practical culture method. The spores were fastened to the 



