78 THE SWEET POTATO. 



and broad leaves are frequent on the plant; B. 1-2, 

 that most large leaves are below four inches in 

 width, but that quite a number measure more than 

 four inches between their extreme tips from side to 

 side. Similarly, E. 1-2 means that the stems occa- 

 sionally attain a diameter of A of an inch, but that 

 most of the stems are less than A of an inch thick, 

 and a few even as little as or less than l^ inch. 

 These peculiarities of some varieties will rather help 

 than hinder in the work of determining them. 



Hoiu to Use the Key. 



The plants should be examined in the field, under 

 normal conditions. The tubers may as well be 

 examined after they are mature, as they show the 

 details better than immature ones. 



Given a plant which was received under some 

 unfamiliar name, and it is to be determined whether 

 it is an old variety appearing under a new name. 

 The leaves are cut. That gives us A. — 1. Most of 

 the later, full-grown leaves measure more than four 

 inches across at their widest points, i. e., from tip 

 to tip of the most spreading lobes. That means 

 B. — 2. The full-grown stems are shorter than four 

 feet. So we put down C. — 2. As the stems are 

 green with purple marks around the axils of the 

 leaves, we have D. — 2. The full-grown stems meas- 

 ure y\ of an inch at their thickest point, which is 

 expressed by E. — 2. The purple star is clear and 

 the lower surface of the vein is purple, which gives 

 us F. — 1 and G. — 1. As a few of the younger leaves 

 show a few scattered hairs on the midrib, and some 

 of the older leaves have no hair at all, we express 

 that by H. — 2-3. The tubers we find to be white 

 outside and inside, which means I. — 1 and J. — 1. 



