38 



BOTANY: HARRIS AND SINNOTT 



PROC. N. A. S. 



The form of the frequency distributions for two of the lines is shown in 

 diagram 3. The epicotyl of the hemitrimerous is in essentials of anatomy 

 identical with that of the dimerous seedling. 



Not only are there marked differences in the actual number of bundles, 

 but the variability of bundle number changes from region to region of 

 the seedling, and differs in the three seedling types. Whether judged by 

 range, standard deviation or coefficient of variation, the variability of 

 bundle number in the central region of hypocotyl tends to be distinctly 

 higher in the dimerous than in the trimerous plantlets; but in the epicotyl 

 just the reverse is true, the variability of the trimerous plantlets exceeding 

 that of the dimerous. These differences are conspicuous in diagrams 2 



DIAGRAM 2 



Percentage frequency distribution of number of bundles in central region of hypocotyl 

 in dimerous and trimerous seedlings. Abscissae represent bundle 

 numbers, ordinates represent percentage frequencies. 



and 3. In the first case it is the dimerous plantlets, in the second case it 

 is the trimerous ones which show the greater variability. Apparently thisi 

 is due to differences in the number of intercalary bundles in the hypocotyl ;; 

 and to the extent of division of the bundles in the epicotyl, of the two type* 

 of seedlings. 



The coefficients of correlation between various bundle systems alsc 

 differ widely. In both trimerous and dimerous seedlings there is a nega 

 tive correlation between the number of primary double bundles and the 

 number of intercalary bundles at the base of the hypocotyl. Thus the 

 number of intercalary bundles is smaller in seedlings with larger number; 

 of primary double bundles and vice versa. This result for seedlings of the 



