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AMERICAN JOURNAL OF BOTANY 
[Vol. 8, 
hypocotyl is apparently significantly higher than that between primary 
double bundles and total bundles in the hypocotyl.- 
The fact that the number of bundles in the central region of the hypo- 
cotyl is about equally correlated with the number of primary double bundles 
and with the number of intercalary bundles at the base of the hypocotyl 
shows that both types of bundles are of about equal significance in de- 
termining the number of bundles in the central region of the hypocotyl. 
From the foregoing discussion it is clear that there is a rather close re- 
lationship between number of bundles at the base and the number in the 
central region of the hypocotyl. This might, we believe, have been ex- 
pected on a priori morphological grounds. The interesting feature of the 
results seems to be that the correlations are not larger. The results show 
that there is a very large amount of irregularity in the division of primary 
strands or in the formation of intercalary bundles, or in both, as one passes 
the short distance from the base of the hypocotyl to the central region. 
Correlation between Bundle Number in Different Internodes 
The data available for a consideration of the problem of the correlation 
between bundle number in adjacent internodes cover (a) the correlation 
between the three classes of bundles at the base of the hypocotyl [primary 
double bundles (^), intercalary bundles {i), and total bundles (Z?)] and the 
number of bundles in the central region of the epicotyl; and (b) the correla- 
tion between the number of bundles in the central region of the hypocotyl 
and in the central region of the epicotyl. 
(a) The coefiicients showing the relationship between the numbers of 
primary double bundles, of intercalary bundles, and of total bundles at 
the base of the hypocotyl, and the number of bundles in the central region 
of the epicotyl, appear in table 3. 
The regression equations showing the actual change in number of epi- 
cotyledonary bundles associated with variation in the number of primary 
double bundles are given and are represented with the empirical means of 
arrays on diagram i for trimerous plants and on diagram 2 for dimerous 
plants. 
The graphs for the theoretical lines and the empirical means ior the 
number of bundles in the epicotyl of both normal and abnormal plants show 
relatively little relationship between the number of bundles at the base of 
the hypocotyl and the number in the epicotyl. The differences in the slope 
of the lines for primary basal bundles and the number of bundles in central 
regions of hypocotyl and epicotyl show in a most striking manner the dif- 
4 In line 75 the range of primary double bundles is only 3 while that of intercalary 
bundles is 6. In line 139 the primary double bundles fall in two classes only, with but 3 of 
the 305 frequencies on 5 as compared with 302 on 4 bundles. The correlation coefficient 
in such a case can have but little value. In line 143 practically all of the primary double 
bundles fall in two classes while the intercalary bundles are limited to three classes. 
Irregularity of results must be expected under such conditions. 
