Curtis : Turgidity in Mycelia 5 



chamber was also constantly kept saturated and the drying up of the 

 drop prevented. Having selected from the drop culture a plant for 

 testing, the cover glass was quickly freed from all fluid possible by 

 means of the feathered edge of blotting paper, washed in the so- 

 lution to which it is to be transferred, placed in a Stender dish and 

 covered with the fluid after the manner described for germinating 

 the spores. This insured an immediate action of the substratum 

 and, owing to the relatively large volume of the substratum, it is not 

 subject to any material change through the metabolism of the plant 

 or the diffusion of any portion of the previously used culture fluid 

 which might still cling to the cover glass through the capillarity 

 of the paper or mycelia. Of course when the period of recovery 

 from a change was short it was only necessary to wash the culture 

 in the fluid to which it was to be transferred and mount it 

 on the damp chamber in a fresh drop of this fluid. Knowing, by 

 experiment, approximately when the plants would recover from the 

 change of substratum, the cover glass was wiped dry, leaving a 

 hanging drop on the mycelia, and placed on the damp chamber. 



It was possible to determine the exact moment of renewal of 

 growth after a change of substratum owing to the fact that this was 

 announced by the enlargement of the apices of the hyphae, which 

 were very constant and characteristic features. The turgidity of the 

 plant was tested at this moment, although the swelling would go 

 on for varying lengths of time, amounting in some cases to 10 or 

 15 minutes before a branch or usually branches would appear that 

 increased the length of the hyphae. 



Every precaution possible was exercised to secure accurate 

 measurements of the turgidity. With the first sign of the en- 

 largement of the apex the cover glass was freed of the fluid and 



urn 



immersed in the plasmolyzing fluid, isotonic solutions of sod 

 nitrate being used. A stock of .the various percentages required 

 was made up and used through all the experiments, and fresh 

 volumes were taken from these jars for each experiment. The 

 turgor force of a plant recovering from a change was always com- 

 pared at the same time with the turgor force of a plant that had 

 germinated and grown in the same strength of fluid to which the 

 trial plant had been changed. In this way two plants in the same 

 condition of development were compared, the one with the turgor 



