AMERICAN VARIETIES OF SWEET POTATOES. 



mine to which of the three groups a given specimen belongs and then 

 to read the descriptions of varieties until one is found which fits the 

 specimen. This is a tedious and cumbersome method, although great 

 credit is due the originator of this system, for it introduced some 

 order into the previous chaotic condition. It is not possible, however, 

 to identify many varieties without taking into consideration many 

 points other than the shape of the foliage. The description given to 

 the varieties is not sufficient to identify most varieties now grown. 



Another classification of sweet-potato varieties that has been pub- 

 lished is the one worked out by Groth (26) . In this system the follow- 

 ing factors are considered in making the key : 



A. Shape of leaf. O. Color of lower surface of veins. 



(1) Cut. 



(2) Round. 



(3) Long. 



(4) Broad. 



(5) Mixed (round and lobed). 



B. Size of leaf. 



(1) Small (less than 4 inches 



across). 



(2) Large (more than 4 inches 



across ) . 



C. Length of stem. 



(1) Long (more than 4 feet 



long). 



(2) Short (less than 4 feet 



long). 



D. Color of stem. 



(1) Green (with or without 



brownish areas). 



(2) Green (with purple around 



the axils of the leaves). 



(3) Greenish brown to purple. 



(4) Purple. 



E. Size of stem. 



(1) Thin (less than one-eighth 



of an inch in diameter). 



(2) Thick (more than one-eighth 



of an inch in diameter, 

 often three-sixteenths or 

 more). 



F. Presence or absence of star. 



(1) Star present. 



(2) Star absent. 



While most of these characteristics are very important, some of 

 them vary so much under different environmental conditions that 

 their use in a key is of doubtful value. The size of the leaf and size 

 and length of the stem vary so much under different soil and climatic 

 conditions that measurements made under one set of conditions do 



(1) Vein purple. 



(2) Midrib pinkish in some old 



leaves. 



(3) Purple spot at base of mid- 



rib. 



(4) Veins all green. 



H. Arrangement of hair on the upper 

 surface of the leaf, if any. 



(1) Hair all over. 



(2) Chiefly on tips and along 



veins. 



(3) Absent. 



/. Outside color of the roots. 



(1) White. 



(2) Yellow, golden, or bronze. 



(3) Yellow, red, or pinkish. 



(4) Red or purple. 



J. Color of flesh of the roots. 



(1) White. 



(2) Cream colored or yellowish 



white. 



(3) Pinkish white or pinkish 



yellow. 



(4) Pinkish orange. 



(5) Marked with purple. 

 Distinctness of wood elements in 



the root. 



(1) Distinct. 



(2) Blurred. 



(3) Not visible. 



K 



