172 



CARL DOWNEY LA RUE 



mycelium. Thus far the form has remained distinct for two generations, 

 and will be studied further in the near future. If it continues to show 

 distinctive characters it will have to be considered as a mutation, though 

 one which affected fewer characters than the one encountered in experi- 

 ment 1. More detailed statements concerning both these mutations will 

 be presented in another publication. 



TABLE 8 



Mean spore lengths of cultures grown in experiment 3. One culture was grown in each line 

 in each generation. Each mean is based on 100 measurements. Measurements in fj,. 



Difference between plus-selected line and minus-selected line =0. 390 +0.328/-1. 



Experiment 4 



It was originally intended that this experiment should be carried on for 

 an extended period of time. In order to lessen the labor required, some 

 changes were made in the method which had been used in experiment 3. 

 The spores were selected and grown in the same manner as in experiment 3 

 but the cultures of each generation were not measured. Instead it was 

 planned to measure them only from time to time to determine whether 

 or not the plus and minus lines were diverging one from another. Un- 

 fortunately only a few selections had been made before the writer left 

 Sumatra. The strain used, No. 5, which was isolated from a leaf spot of 

 cocoanut palm and had been successfully grown for nine generations in 



