220 



TAXONOMIG STUDIES IN THE GE^aJS CERASTIUM : I 



the variation of this character was considerable, the standard errors large, and the 

 distribution not normal. A graphical representation of the measurements of 136 samples 

 of C. pumilum is shown in the histogram (Fig. 3). The distribution of this character 

 approximates to bimodality, except that one half of one mode is not represented. It was 

 difficult at first to account for this type of distribution but further examination of the 

 specimens showed that two uncorrected variables v/ere in fact being measured. Because 

 of the difficulty of determination there appears to be a tendency to collect C. pumilum 



FIG. 3 



a- 



10- 



>- 

 z 



Ui 



6 - 



10 



3.0 



30 



SO 



ro 



capsule/calyx ratio 



&0 



90 



in a young state so that many specimens have only immature capsules. These are shorter 

 than the fully mature capsules, and in any collection of these plants there will tend to be a 

 greater proportion of capsule/calyx ratios approaching unity than would be found if all 

 the specimens had fully mature capsules. The measurements in fact give an estimate 

 not only of the range in size of the mature capsule/calyx ratio but also the range of 

 maturity of the samples. Since many of the specimens being used were so young that 

 fully mature capsules were lacking, it was not possible to use this character further. 



