SELECTION WITHIN PURE LINES OF PESTALOZZIA 



153 



tubes were put into one rack so that all might be subject to the same 

 general environmental conditions. 



When the mycelia had all grown and the spores were mature, 100 spores 

 of each culture were measured and the mean spore length, or mean append- 

 age length, as the case might be, was computed. By trial it was found 

 that 100 measurements were sufficient to secure a smooth distribution 



TABLE 1 



Typical frequency distribution of measurements of spores and spore appendages from different 

 cultures of Pestalozzia Guepini. Measurements in (JL. 



curve and a mean with a satisfactorily small probable error, so with some 

 exceptions, where a few more spores were taken, one hundred from each 

 culture were measured. Typical distributions are shown in table 1. 



After the twenty cultures were measured the one with the greatest mean 

 spore length was chosen as the starting point for plus selection. Similarly 

 the culture with the smallest mean spore length was taken as the beginning 



GENETICS 7: Mr 1922 



