80 THE SWEET POTATO. 



the two cannot be told apart in the field, unless one 

 dig for the tubers. 



2. It can be used with incomplete specimens. If 

 a certain character cannot be determined from the 

 material on hand, the space reserved for it may be 

 left blank, and the next character taken up. One is 

 not continually before alternatives which may be at 

 the time unanswerable. It is likely that the deter- 

 mination is possible even without that character. 



3. It is more convenient to the non-scientist. In 

 the determination of all varieties the same process 

 is gone through, and once that process is learned by 

 heart it need not be changed again for the deter- 

 mination of the next variety. 



4. It is flexible. The writer is certain that he 

 has not studied all varieties existing. New varie- 

 ties can be easily catalogued and inserted in the list 

 by anyone. In the ordinary key the advent of a new 

 variety necessarily causes confusion, as it not only 

 could be wrongly determined itself, but would also 

 interfere with the determination of other varieties 

 which might agree with it in the critical characters. 

 A considerable number of new varieties would make 

 an ordinary key useless, while this key provides for 

 all. Should other characters be found which would 

 aid in the determination, they could simply be 

 entered under subsequent letters, L — , M — , N — , 

 etc., without interfering in the least with the work- 

 ing of the key. 



D. Alphabetical List of Formulas. 



Al B2 Cl Dl El F2 G4 HI 13 J3 Kl = Belmont. 

 Al B2 Cl Dl El-2 F2 Gl -f- 3 H3 12 J2 K3 — Kala. 

 Al B2 Cl Dl El-2 F2 G4 HI 12-3 J3 Kl = Georgia, 

 Al B2 Cl D2 E2 Fl Gl H2 II .Jl K3 = White Gilk. 

 Al B2 Cl D2 E2 Fl Gl H2 12 .J2 K3 = John Bvirnet. 



