H. M. Leake 



241 



will afford a means of separating the impure forms, nor is it a method 

 which becomes available till after the work of fertilisation is long over. 

 At present no method of discriminating with certainty between the 

 pure and impure forms during the major portion of the life of the plant 

 has been discovered. 



Correlation. 



One instance of correlation has already been dealt with in section .3 (d) 

 on the type of branching and the length of the vegetative period. In 

 this instance the correlation was seen to depend on a recognisable 

 feature — the flowers are only formed as a development of the apical 

 buds of the sympodia the growth of which is carried on by the main 

 lateral bud. In the present section reference will be made to two 

 other instances of correlation, but in them the feature on which the 

 interrelation between the two characters depends is thus not recog- 

 nisable. 



Fig. 3. 



There appears to be complete correlation between the size of the 

 petal and the colour of the flower. If the petals be white in colour 

 they will be small and hardly project beyond the bracteoles ; on the 

 other hand, if the colour be yellow, they will be large in length, about 

 twice that of the bracteoles (vide Figs. 3 and 4)*. 



> The difference is well shown by a comparison between Plates 14 a and 16 Watt (20). 



