35O AMERICAN JOURNAL OF BOTANY [Vol. 8, 



hypocotyl is apparently significantly higher than that between primary 

 double bundles and total bundles in the hypocotyl. 4 



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 (&)] 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 coefficients 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 for 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. 



