SELECTION WITHIN PURE LINES OF PESTALOZZIA 



173 



culture with the results shown in figures 1 and 2, and in table 9, did not 

 thrive well in Michigan, even when kept in a constant-temperature room, 

 so after six selections the experiment was discontinued. While the experi- 

 ment included fewer selections than is desirable, a large number, perhaps 

 the majority, of selection experiments have been carried no farther, and 

 no apology need be made for presenting the results. These are shown in 

 table 10 and the measurements of the selected parent spores are presented 

 in figure 10. 



The spores selected, on the basis of spore length, as parents of the plus 

 and the minus lines, were significantly different from each other in every 

 generation, so that there can be no doubt that real selections were made. 



TABLE 9 



Mean spore lengths of cultures of strain 5, grown prior to the initiation of experiment 4. Measure- 

 ments in p. 



The cultures were removed from Sumatra after three minus selections 

 and two plus selections had been made. The fourth, fifth, and sixth selec- 

 tions of the plus line show no decrease in spore size following this change 

 of climate, since they are all at least equal in size to the third selection, 

 and the sixth selected spore equals the size of the first and second parent 

 spores of the line. In the minus line, however, the third, fourth, and fifth 

 selections show a decided decrease in spore size. The sixth selected 

 spore is equal in size to the second, but it should be noted that another 

 chosen spore of precisely the same size as the fifth selected spore failed 

 to grow. It is rather uncertain whether any of these changes may be 

 attributed to climatic changes. 



GENETICS 7: Mr 1922 



