SELECTION WITHIN PURE LINES OF PESTALOZZIA 



147 



The total range of mean length of spores for all the strains of P. Guepini 

 isolated by LARUE and BARTLETT (1922) was from 19.9ju to 28.3/z. Figure 

 1 shows the polygons of variation in spore length for a few representative 

 strains. Mean appendage lengths of the strains ranged from 10.9jit to 

 30.0/i. The polygons for variation in appendage length are shown for 

 six representative isolations in figure 2. More complete data, which can- 

 not be reproduced here, are given in the paper already cited. In view of 

 the large number of strains which exist within the species, this fungus is a 

 very favorable organism for use in making an attempt to develop still 

 other strains by the selection of variant spores. 



4-0 



1 



35 

 30 

 25 

 20 

 15 

 10 



13 



\ 



14 16 18 20 ^^ 24 26 28 30 32 34 36 3G 



FIGURE 1. Polygons of variation in spore length for six strains of Pestalozzia Guepini. 

 The ordinates are percentages; the abscissae, lengths in p. 



It is essential that any organism which is to be employed in the study 

 of the selection problem be easy to cultivate and in this respect P. Guepini 

 is admirable. It will grow readily and rapidly on almost any common 

 nutrient agar and can also be grown on sterilized leaves, twigs and fruits 

 of its common hosts. In Sumatra usually only about four days time was 

 needed to develop the fungus from spore to the fruiting condition. In 

 Michigan a slightly longer time was needed to secure spores even when 

 the fungus was kept at a temperature approximately the same as that of 

 Sumatra. Strong light appears to inhibit the growth of the young myceli- 

 um, but exposure to light after the mycelium is about three days old seems 

 to hasten the production of spores. 



GENETICS 7: Mr 1922 



