SELECTION WITHIN PURE LINES OF PESTALOZZIA 



171 



The means of means of all the cultures in the two lines when compared 

 are found not to be significantly different. The upward and downward 

 swings have had the same total effect in one line as in the other though the 

 different lines have scarcely paralleled each other at all during these swings. 

 Experiment 3, then, entirely substantiates the results gained in experi- 

 ments 1 and 2, and shows that the selection of visible characters within a 

 pure line is no more effective in producing distinct groups than selection 

 on the basis of progeny. 



In the course of experiment 3 an aberrant form appeared, which seems 

 to be a mutation. This arose in the plus line in the seventeenth generation. 



FIGURE 9. Graphs of the spore lengths of cultures grown in experiment 3. P shows the 

 cultures of the plus line; M those of the minus line. The ordinates are lengths in n; the abscissae, 

 the generations of the experiment. 



In regard to length of spores and of spore appendages it is identical with 

 strain 17 from which it arose. However, it has vegetative characters 

 quite distinct from those of strain 1 7 and this makes it appear very different 

 to the naked eye. Strain 17 produces a very small amount of mycelium 

 on the surface of the agar substratum, which becomes almost completely 

 covered with a black, slimy mass of spores. The new form produces a 

 thick felt of mycelium all over the surface of the agar, and sporulation is 

 much more tardy than in strain 17. The spores are produced in small 

 black masses which are rather sparsely scattered over the surface of the 



GENETICS 7: Mr 1922 



