VOL. 7, 1921 



BOTANY: HARRIS AND SINNOTT 



39 



same (external) morphological type is in agreement with those obtained 

 by a comparison of seedlings which are externally dimerous and trimerous, 

 since the latter frequently have a larger number of primary double bundles 

 but a smaller number of intercalary bundles than the former. In both 

 types of seedlings variation in the number of intercalary bundles is the 

 primary factor in determining variation in the total number of bundles at 

 the base of the hypocotyl. 



Turning to the problem of the interrelationship of bundle number at 

 different levels in the seedling we find that there is a substantial correla- 



12 13 /4 IS 16 11 IB 19 20 21 



12 13 /4 /S 16 11 18 /9 20 21 



DIAGRAM 3 



Percentage frequency distributions of total bundle number in the central region of the 

 epicotyl of dimerous and trimerous seedlings of two lines. Abscissae represent 

 bundle numbers, ordinates represent percentage frequencies. 



tion between the numbers of the three classes of bundles primary double 

 ; bundles, intercalary bundles, and total bundles at the base of the hypo 

 cotyl and the number of bundles in the central region of the hypocotyl. 

 In the normal seedlings the coefficients average +0.509 for number of 

 primary double bundles and number of hypocotyledonary bundles, +0.629 

 for intercalary bundles and hypocotyledonary bundles, and +0.813 for 

 total bundles and hypocotyledonary bundles. In the trimerous plants 

 these correlations average +0.381, +0.238 and +0.598, respectively. 

 The correlations for normal plantlets are practically without exception 

 higher than those for abnormal seedlings. 



The correlations between the number of bundles in the hypocotyl 

 (both basal region and central region) on the one hand and the number of , 



