72 THE SWEET POTATO. 



greenhouses and the soil of a sandy New Jersey- 

 field, nor the difference between the comparatively 

 dry growing season of the summer of 1905 and the 

 extremely wet and hot season of 1906, affected the 

 value-of the size of the leaf as a characteristic in the 

 least. 



All varieties begin the season's growth with small- 

 sized leaves. The largest leaves do not appear until 

 after two or three months of growth, and therefore 

 all references to size apply only to those later large 

 leaves. 



The ''small-leaved" varieties never have normal 

 leaves measuring over four inches in width from 

 tip to tip. In fact, most of their leaves are less than 

 three inches wide. These "small-leaved" varieties 

 are, however, most given to fasciation, and fasciated 

 branches may have larger leaves. These have not 

 been considered in the key. 



The "large-leaved" varieties have many of the 

 later large leaves measuring over four inches at 

 their widest part. Some varieties commonly grow 

 leaves six to seven inches across. 



A character as definite and as easy to determine 

 as the shape and size of the leaves is the length of 

 the stems. 



The bunch varieties and other "short-stemmed" 

 varieties never have stems measuring as much as 

 four feet long, even in a wet season. 



The color of the stems is another very helpful 

 character which is easily determined. 



Some varieties have entirely green stems with at 

 the most a few blotches of brownish sunburn. These 

 are classed together as "green-stemmed." Others 

 liave green stems which bear small purple marks 

 around the axils of the leaves, i. e., around the base 



