IO2 AMERICAN JOURNAL OF BOTANY 



of the hypocotyl are quite lost in the cotyledonary nodal vascular complex 

 and thus do not affect the variability of the dimerous plants; and (/&amp;gt;) thai 

 the doubling of the primary epicotyledonary bundles which almost invariablj 

 occurs in the normal seedling may not always take place, at least not at ai 

 low a level as the central region of the epicotyl, in the abnormal type. 



CONCLUSIONS 



The results of the foregoing morphological and biometric analyse 

 justify the emphasis at this point of certain general considerations. 



1. External differentiation such as that which characterizes dimerou 

 and trimerous seedlings of Phaseolus vulgaris is accompanied by profouil 

 differences in internal structure. 



2. Anatomical characters are by no means constant. On the contrary 

 they are very variable even in series of individuals which are genetical 

 highly homogeneous. Morphological investigations based on limits! 

 series of individuals may, therefore, result in inadequate conceptions. 



3. Variation in anatomical structure is not constant for the plant as I 

 whole, but may differ from region to region or from organ to organ. Thu 

 in the regions of the seedling here under consideration, hypocotyl and epi 

 cotyl differ widely in the variability of bundle number. Furthermol 

 differences in variability from organ to organ or from region to region a* 

 not constant, but may be conditioned by other morphological featured 

 To illustrate from the case in hand, the variability of bundle number 

 normal seedlings is higher in the hypocotyl than in the epicotyl. In seed 

 lings with three cotyledons and three primordial leaves, just the reverse i 

 true. These differences in biometric constants are readily understandabl 

 in the light of a knowledge of comparative morphology. 



4. The results of this study emphasize the importance of the use of hot 

 biometric and comparative methods to supplement each other in any attaa 

 upon the problems of general morphology or of morphogenesis. 



