Nov.. 192 1 ] HARRIS AND OTHERS — PHASEOLUS VULGARIS 
429 
It is suggestive to note that the negative correlation between number of 
primary double bundles and number of intercalary bundles demonstrated 
here within seedlings of one class with regard to external structure is also 
evident when we pass from a type of seedling with a smaller to one with a 
higher number of primary double bundles. It has been shown in an earlier 
paper that (a) the number of trimerous seedlings having intercalary bundles 
is generally smaller than the number of dimerous seedlings with these 
accessory structures, and that (b) the average number of intercalary bundles 
is generally smaller in trimerous than in dimerous seedlings. 
= TRIMEROUS 
0 / 2 3 4 5 6 Oil 
/A/TERCALATiy IBU/VULES 
Diagram 2. Regression of number of primary double bundles on number of intercalary 
bundles, at base of hypocotyl. 
2. Relationship between the Total Number of Bundles and the Number of 
Bundles of the Two Types. We may now inquire to what extent the varia- 
tion in the total number of bundles depends upon the primary double 
bundles and to what extent upon the number of intercalary bundles. As a 
first step we determine the correlation between the total number of bundles 
and the number of primary double bundles, and between the total number 
of bundles and the number of intercalary bundles. These results are set 
forth in table 2. 
We note that the correlations between the total number of bundles and 
the number of intercalary bundles are in all cases high, ranging from +.42 
