RELATIVE SIZE OF DIFFFERENT DIVISIONS OF PLANT. 



53 



for the secondaries. In order that a more definite idea may be obtained 

 of the comparative distributions for the different orders of branches, I 

 have prepared the diagrams given in fig. 9. These were made by plot- 

 ting to the same base-unit the percentage frequencies of primary, 

 secondary, and tertiary branches of different sizes, taking all the plants 

 of Series I, II, and III together. In order to smooth out some of the 

 irregularities in the distributions which arise from the relative smallness 

 of our samples, I have doubled the size of the classes given in the tables. 



J530 



•■ ' I i^ '^ ~ -- ' I — >V- ^ *^— '»' ■ 



I-H2 3t+ 5+6 7+8 9+10 11 + 12 13+14 15+16 17+18 19+20 2I+Z2 Z3+Z4 Z5+Z6 27+28 29+30 



Number of whorls per branch 



Fig. 9.— Frequency distributions for length of primary, secondary, and tertiary 

 branches. The ordinates give percentage frequencies and tlie abscissas tlie num- 

 ber of whorls per branch. Primary branches, » ; secondary branches, 

 o ; tertiary branches,® . 



From these diagrams we see clearly the general nature of the varia- 

 tion in the size of branches. The smoothness of the primary and 

 secondary branch curves is remarkable. The most frequently occurring 

 branches, whatever their order, are those having from 1 to 4 whorls. 

 The great range of secondary branches in length is rather surprising. 

 As was to be expected, the proportionate number of branches with 1 or 

 2 whorls increases enormously as we pass from primary to tertiary 

 branches. The diagrams show that the proportionate number of 



