114 



Pearl and Surface. 



Stimulus due to tasseliug continues to exert itself as long- as the upper 

 node is gi'owing. 



The effect of tasseliug upon the growth and variability of the 

 corn plant is not unlike the effect of puberty upon the growth of children. 

 To show the similarity in the form of these variation curves we have 

 calculated the coefficients of variation for the stature of school children 

 from the age of five and one-half years up to eighteen and one-half. 

 These coefficients were calculated from the means and standard deviations 

 given by Boas ('97). The particular data used were the growth of 

 American boys and girls given on pages 1555 and 1566 of his paper. 

 These coefficients are shown in Fig. 4. 



4.0 



Fig. 4. 



55 



75 



95 



11.5 13.5 



AGE IN YEARS. 



Coefficients of variation for the stature of children; 



15.5 



17.5 



boys; girls. 



From this figui'e it is seen that the onset of puberty greatly 

 increases the variability. After the age of about thirteen for girls and 

 fifteen for boys there is a very rapid decrease in the variability until 

 it reaches a point considerably lower than its value before the lieginning 

 of puberty. 



In these respects the effect of puberty is not unlike the effect of 

 tasseliug upon the growth of the corn plant. However, this does not 

 mean that puberty and tasseliug are necessarily analogous. We have 

 already indicated that one of the reasons for the increased growth of 

 the corn plant after tasseling is that the leaves ai'e all formed l)y this 

 time and hence the growth energies are directed towards the elongation 



