VARIABILITY OF SUCCESSIVELY FORMED WHORLS. 



103 



The equation to the straight Hne is, 



2/ = 0.5054 1 1 -0.4442(^) j- 



where I = 6. The fit is a very reasonable one, and clearly a straight 

 line gives a sufficiently good graduation for our present purpose, which 

 is merely to show the general trend of the observations. Out as far as 

 the 9th whorl the scedastic curve is quite regular. I think that there 

 can be no doubt that the secondary-branch whorls follow the same law 

 as those on primary branches in respect to their variability. The varia- 

 tion in leaf-number decreases more and more as successive whorls are 

 formed. 



0.9 



03 



ae 





\i' 



0.5 



0.3 



0.2 



I Z 3 4 5 6 7 8 9 10 II l^ 13 



Whorls 

 Fig. 22.— Scedastic curve for secondary-branch whorls. Series I, II, and III combined. 



We may fairly conclude that what is true of the variability of primary 

 and secondary branch whorls will also be true of whorls on other branch 

 divisions of the plant (tertiaries, etc. ) . On account of the relatively 

 small number of tertiary-branch whorls it is not possible to test the 

 matter directly there. Our results in the previous section of the paper 

 with reference to the mean number of leaves in successive whorls in 

 different divisions of the plant makes it very probable that a similar 

 uniformity prevails with reference to variability. 



Fortunately, we can test the matter directly for main-stem whorls. 

 In table 42 (p. 83) are given, for the combined plants of Series I, II, 



