148 



CARL DOWNEY LA RUE 



When speculation begins the spores are developed very rapidly and in 

 enormous numbers. This is a characteristic exceedingly valuable in 

 biometrical studies, since the variates are produced under as nearly identi- 

 cal conditions as may be found anywhere. By measuring a sufficient 

 number of such spores one can get the whole range of variability induced 

 by the reaction of a given set of environmental conditions with the heredi- 

 tary characters of the organism. In an organism which produces offspring 

 slowly a number of fluctuations in environment must necessarily take place 



> 10 \l 14 16 16 ?0 II 24 26 28 30 32 54 36 40 



FIGURE 2. Polygons of variation in length of spore appendages for six strains of Pestalozzia 

 Guepini. The ordinates are percentages; the abscissae, lengths of appendages in M. 



before a number of individuals sufficient to give a reliable mean is produced. 

 This complicates the situation greatly and the means of two groups of 

 organisms so produced are less readily comparable than those developed 

 in an organism such as Pestalozzia. 



Mention has already been made of the dark color of the three central 

 cells of mature spores of P. Guepini. This color is a valuable index of the 

 age of the spores because it does not fully develop until the spores have 

 reached their full size and the appendages have been fully formed. One 

 can always recognize mature spores at a glance and is thus able to reject 



