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THE AMERICAN NATURALIST [Vol. XLVIII 



seventh leaf has appeared (Fig. 5). It is to be noted that 

 for the first six leaves of type 4, the ratio between mean 

 length and width is 6:2, while for the corresponding 

 leaves of type 3, the same ratio is 5 :2. Once the seventh 



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leaf has appeared, a distinction readily can be made, since 

 in type 3, no sinuses appear, and the leaves, from the 

 seventh to the tenth, might be mistaken for those of 

 simplex (Fig. 5). Later leaves readily can be distin- 

 guished from those of simplex, by the pointed apex, the 

 very shallow sinuses, ending in a sharp tooth, and by the 

 fact that the greatest width of the blade lies above the 

 middle, about one third the length from the tip (Fig. 6). 



This form, which because of its morphological charac- 

 ters on the one hand, and its behavior in breeding on the 

 other, can readily be distinguished from all others, I 

 designate X Capsella Bursa-pustoris atteimata. 



Type 4.— Not only do the first leaves of plants, belong- 

 ing to this type, differ in relative width from the first 

 leaves of plants of rhomboidea and simplex, but there also 



