4 Curtis : Turgidity in Mycelia 



these variations are the expression of different conditions and 

 forces existing in the plant and if the measurement of the turgi- 

 dity is to be of any value it must be determined from plants pre- 

 senting a uniform vigor of growth. It was often a difficult task 

 to find in successive cultures hyphae showing the same vigor and 

 condition of growth. The fluctuations in the rate of growth due 

 in some cases to preparations for branching on the part of the 

 plant and in other instances due to no apparent cause, rendered it 

 difficult to select plants in the various experiments that would give 

 real comparative values. This difficulty presented itself again when 

 changes from one media to another had been made. ' For perhaps 

 the hyphae under observation would not respond to the change 

 for half an hour or longer after others had showed the desired 

 effects. The question then presents itself, How much weight can 

 be given to any measurement in such an instance ? Obviously 

 such conditions necessitated repetition of experiments many times 

 to arrive at any conclusions. 



To secure the most uniform conditions possible the spores, 

 prepared as above described, were germinated in closed Stender 

 dishes, 8 x 4% cm., the cover glasses being just covered with the 

 fluid. By this means the spores and germinating plants were ex- 

 posed to the same atmospheric conditions and always had the 

 same volume of nutrient solution to draw upon, while the solution 

 could not materially absorb or evaporate water — factors of vital 

 importance to the success of the work. By removing the covers 

 of the dishes the cultures could readily be examined on the table of 

 the microscope without danger of disturbing them and when 

 found ready for use the cover glass was removed, carefully freed of 

 the fluid with a blotter save about the hyphae and studied in a 

 hanging drop over a damp chamber. In all experiments the 

 damp chamber (made from a piece of thick cardboard) was placed 

 in a Stender dish, the bottom of which was covered with the same 

 solution as used in the hanging drop. I found this to be of the 

 greatest importance for if there was any considerable variation in the 

 concentration of the hanging drop and the fluid of the damp 

 chamber a very considerable change would result in the con- 

 centration of the hanging drop producing very material alter- 

 ations in the rate of growth and turgor. In this way the damp 



