346 AMERICAN JOURNAL OF BOTANY [Vol. 8, 



section of table I. The straight-line equations showing the regression of 

 the number of bundles in the central region of the hypocotyl are recorded 

 and represented graphically on diagram 3 for trimerous seedlings and on 

 diagram 4 for dimerous seedlings. These diagrams, like the two preceding, 

 also give the regression equations and their graphic representation for the 

 epicotyl which will be discussed in a subsequent section. 



The correlation coefficients are positive in all cases, and with one ex 

 ception may be considered statistically significant. They show, however, 

 a considerable irregularity from line to line, presumably because of the 

 varying range and distribution of number of intercalary bundles. The 

 average value of the coefficient is +.2376 for trimerous seedlings and 

 + .6290 for dimerous seedlings. 



Turning to the graphs, we may note that for the dimerous plants the 

 agreements between the empirical and the theoretical means are very good 

 indeed. The slope of the lines for the hypocotyl is very steep. 



The graphs for the trimerous plants show far greater irregularities be 

 cause of the generally small number of the strands but the occasional oc 

 currence of plants with a larger number. Reference to the tables will 

 show that in line 75 there is one seedling with 6 intercalary bundles whereas 

 the remaining 141 seedlings have only o, I, or 2 intercalary bundles. In 

 line 93 there is only one seedling with more than 2 intercalary bundles and 

 it has 4. In line 98 all the frequencies with two exceptions fall on o or I 

 intercalary bundle. 



The correlations and equations have been recalculated, leaving these 

 extreme cases out of account. The regression straight lines based on all 

 the material are represented by solid lines. Those in which the extreme 

 class were omitted are represented by broken lines. 3 The removal of these 

 aberrant cases has increased the agreement between the observed and the 

 theoretical means but the fit is still far from satisfactory. The only con 

 clusion which can be drawn from these diagrams is that there is a con 

 siderable degree of positive correlation between the number of the inter 

 calary bundles and the number of bundles in the hypocotyl. 



Total Basal Bundles and Mid-region of Hypocotyl 



The correlations between total bundles (primary double bundles -f in 

 tercalary bundles) at the base of the hypocotyl and the number of bundles 

 in the central region of the hypocotyl, r b h, are show r n in the third section of 

 table i. The straight-line regression equations are given and represented 

 graphically as the lower figures in each panel of diagram 5 for trimerous 

 seedlings and diagram 6 for dimerous seedlings. 



As might be expected on a priori grounds, these coefficients agree with 

 those for primary double bundles and for intercalary bundles in sign, and 



3 For the curtailed series the regression equations are: Line 75, H = 12.194 + - 

 Line 93, H = 12.238 + 0.462 7; Line 98, H = 12.030 + 0.473 /. 



