20 DIMORPHIC LEAVES IN RELATION TO HEREDITY. 



TWO TYPES OF DIMORPHISM OF LEAVES IN COTTON. 



Tlic (liinorphism of leaves in Hibiscus is of the same type as that of 

 tlie narrow-leaved "okra" cottons, as already indicated. But there 

 is another type of dimorphism of leaves in cotton, connected with a 

 definite dimorphism of the branches. The leaves of the fruiting 

 branches of cotton are smaller than those of the main stalk and 

 vegetative branches and often have nectaries on only one or two of 



Fig. "J.— Leaf of " I'ark's Own," an "okra" varii-ty of Aiiioricaii Upland cotton. 



(Natural size.) 



the principal veins, even when the leaves of the main stalk and vege- 

 tative bi-anches have three nectaries with nmch regularity. 



The dimorphism is not so easily recognized in the blades of the 

 leaves, because of the general freedom of variation in sizes and shapes, 

 but ai)])ears much more definite when attention is given to the 

 stipules. On the nuiin stalk and the vegetative branches the leaves 

 have the two stipules ecjual in size and narrowly lanceolate or strap 



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