28 VARIATION AND DIFFERENTIATION IN CERATOPHYLLUM. 



VARIATION IN WHORLS ON THE MAIN STEM. 



The frequency distributions for main-stem whorls of the different 

 plants and series are shown in table 5 (page 27) . In this table all the 

 divisions of the main stem are combined. 



In order to bring out more clearly the form of these distributions, 

 and to facilitate comparison, the frequency polygons for the totals of 

 each of the six series have been plotted and are shown in fig. 6. All of 



Leaf number 

 Fig. 6.— Frequency polygons for variation in leaf-number in wliorls on the main stem. 



Series I, »— — ~— — ; Series II, o — ^ ; Series III, e ; Series IV, 



^ —.; Series V, o — ; Series VI, x-o----0"--o. The ordinates give percent- 

 age frequencies. 



these polygons are so plotted as to have the same area. The scale of 

 the drawing is approximately the same as that of fig. 3 (p. 18) so that 

 direct comparisons may be made. 



From the distributions and polygons it is seen that on the main 

 stem the most frequently occurring whorls are generally those having 

 10 leaves. Series V is the only exception to the rule, and in that case 

 whorls with 9 or 10 leaves are within the error from random sampling 

 equally frequent. There is distinctly less "scatter" in the main-stem 



