6 Curtis : Turgiditv ix Mycelia 



normal to the solution in which it was growing and the other had 

 so adjusted its turgor to this same concentration of the substratum 

 that growth became possible. It was found, after trying a certain 

 percentage of the plasmolyzing solution on a plant without produc- 

 ing plasmolysis that any subsequent tests with higher strengths were 

 unreliable, giving too high values to the turgor force. This is 

 doubtless due to the fact that a solution too weak to plasmolyze 

 does cause a concentration of the cell contents as is seen from the 

 reduced size of the hyphae. One of the surprising features of the 

 work was the variability of the turgidity, so that it was not at all 

 safe to rely upon any determination of the turgor force of plants 

 grown in a given concentration as a basis for comparison of plants 

 changed to this concentration ; as mentioned above, a test plant 

 was always used as a check upon all measurements. This varia- 

 bility of the turgidity was also observed while working with Prof. 

 Pfeffer, for whose courtesy in extending to me the privileges of 

 the laboratory, I wish to return thanks. 



Some of the results of the experiments upon Mucor will be found 

 in the first table. The first column shows the average tempera- 

 ture of the day on which the experiment was made. In the sec- 

 ond column is the record of the changes of the substratum ; thus 

 0-4 indicates that the spores were grown in a simple nutrient 

 solution and transferred to a nutrient solution containing 4^ 

 KN0 3 . The third column shows the time elapsing after the 

 change before growth appeared. For example, in the first exper- 

 iment the culture was transferred at 8.10 to a 4^ KNO. nutrient 

 solution. Growth ceased till 10.13, or growth was renewed after 

 two hours and three minutes. The turgidity in percentages of 

 NaN0 3 is found in the fourth column. A — after a number indi- 

 cates that this percentage did not plasmolyze as perfectly as in the 

 case of the plant used as a check and for comparison. A -f- sig- 

 nifies the reverse condition, and that the plasmolysis was more se- 

 vere than in the check plant. N. P. indicates that the percentage 

 used failed to plasmolyze at all the hypha. The last column in- 

 cludes the measurements of the turgidity of the plants used as checks 

 and for comparison with the plant subject to the change of sub- 

 stratum. Considering the second experiment, 18 in the fifth 

 column indicates that this was the turgor force of plants germin- 



