74 



AMERICAN JOURNAL OF BOTANY 



[Vol. 



associated with an increase of fifty percent in the number of cotyledons anc 

 leaves. The distributions show, however, that this is only an incomplete 

 and to some extent an erroneous, statement of the condition. In th&amp;lt; 

 dimerous seedlings the modal number of primary double bundles is 4, and al 

 departures from the modal number are higher. In the trimerous seedling! 

 the modal number is 6, and the departures may be in either the positive 01 

 the negative direction. The frequency distribution for the dimerous plantf 

 is therefore wholly skew, forming a typical J-curve; that for the trimerom 

 plants more or less symmetrical, 8 but with departures occurring chiefly a; 

 smaller numbers of bundles. 



The variation of primary double bundle number in dimerous and trim 

 erous plants is, therefore, transgressive. The number of externally dimerous 

 seedlings which might be considered to be anatomically trimerous, and tin 

 number of trimerous seedlings which might on anatomical grounds b( 

 considered dimerous is, however, very small. 



Turning to the physical constants in table 4, we note that the meat 



TABLE 4. Statistical constants for number of primary double bundles at base of hypocotyl 0j 

 trimerous plants and their normal controls 



8 Line 139 is probably only an apparent exception to this rule. In both dimerous an 

 trimerous seedlings variations from the modal class are extremely rare, and variation 

 above the modal class have not been found in the 106 trimerous seedlings of this lin 

 sectioned. 



