pi., 1921] 



HARRIS AND OTHERS SEEDLINGS OF PHASEOLUS 



101 



In both types of seedlings, but more frequently in the normal ones, 

 aditional or intercalary bundles appear in the hypocotyl, either de novo 

 oils a result of division of the primary strands. 



The following constants 13 (table 19) for bundle number (at the different 

 leels studied) epitomize the differences which characterize the two types 

 01 seedlings. 



TABLE 19 



The variability of root pole number is distinctly higher in trimerous than 

 idimerous seedlings, because of the fact that in all seedlings a four-poled 

 ccidition is characteristic of the main root system and prevails even in 

 tf trimerous forms up to within a few millimeters of the base of the hypo- 

 ccyl. Sections in the upper root region in such seedlings therefore show a 

 ccisiderable number of four- and five-bundled individuals. 



The number of intercalary bundles is highly variable in both seedling 

 tj&amp;gt;es. The standard deviation is distinctly larger in the dimerous forms, 

 b : because of the generally lower average number of intercalary bundles in 

 tmerpus seedlings, the relative variabilities as measured by the coefficient 

 o:variation are higher in the trimerous type. 



In the central region of the hypocotyl the variability of bundle number, 

 bdi absolute and relative, is far higher in the dimerous seedlings, due in 

 Mge part to the generally higher standard deviation of the number of 

 irercalary bundles in the dimerous type. 



In the central region of the epicotyl just the reverse is true, the varia- 



y of bundle number being higher in the trimerous than in the dimerous 

 sedlmg. This is evidently due to the facts (a) that the intercalary bundles 



1 Data for number of root poles are available for only three of the five lines. 



