352 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8. 
As explained above (p. 346), the slopes for the trimerous seedlings are 
very greatly influenced by certain aberrant individuals. When these are 
removed we obtain the equations represented by the broken lines in the 
figures.^ The results for the relationship between the number of inter- 
calary bundles and the number of bundles in the epicotyl indicate a positive 
correlation in all 3 cases when the one extreme plant is removed. 
(3) The coefficients of correlation between total bundles (double bundles 
plus intercalary bundles) at the base of the hypocotyl and the number of 
bundles in the central region of the epicotyl, f^g, are shown in the third 
section of table 3, and are represented graphically in terms of regression 
in the upper figures of each panel of diagram 5 for trimerous seedlings and 
of diagram 6 for normal seedlings. The very gentle slope and the differ- 
ences in direction of the lines for the epicotyl of the trimerous plants, to- 
gether with the irregularity of the empirical means, serve to emphasize 
the slightness of the relationship between total bundles at the base of the 
hypocotyl and the number of bundles in the central region of the epicotyl. 
In the normal plantlets the means are less irregularly distributed about 
the theoretical lines, but the slope of the lines is very slight, and in one case 
the regression slope has the negative sign. 
Turning to the correlation constants for more direct numerical com- 
parison, we note that three of the ten constants are negative. The general 
average is +.0456 for the trimerous and +.1228 for the dimerous seedlings. 
Looking back over diagrams 1-6, one cannot but be impressed by the 
difference in the slope of the lines showing the changes in number of bundles 
in the hypocotyl and in the epicotyl respectively associated with variations 
in the number of bundles at the base of the hypocotyl. The lines for the 
hypocotyl, without exception, indicate an increase in the number of bundles 
in the central region of the hypocotyl with an increase in the number of 
bundles at the base of the hypocotyl. The lines for the epicotyl occasionally 
show a decrease. Furthermore, the slopes of the lines for the hypocotyl 
are in general conspicuously steeper — thus indicating closer dependence 
upon the number of basal bundles — than those for the epicotyl. 
Turning to table 4 for a numerical comparison of the correlations be- 
tween the systems of bundles on the same side and on different sides of the 
cotyledonary node, we note that without exception the coefficients of corre- 
lation measuring the interrelationship between the number of vascular 
elements at the base of the hypocotyl and in the central region of the epi- 
cotyl are markedly lower than those measuring the correlation between the 
number of vascular elements in the base of the hypocotyl and in the central 
region of the hypocotyl. 
(b) We now have to consider the problem of the correlation between 
the numbers of bundles in the central regions of the hypocotyl and of the 
5 When the extreme cases are omitted the equations are: Line 75, E = 15.378 + 0.591 /; 
Line 93, E = 15.670 + 0.096 /; Line 98, E = 14.840 + 0.394 J. 
