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 this 
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 types 
of seedlings. 
The coefficients of correlation between various bundle systems also 
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 numbers 
of primary double bundles and vice versa. This result for seedlings of the 
