16 MASS. EXPERIMENT STATION BULLETIN 431 



Key to Varieties 



Since it is a tedious and time-consuming job to compare an unfamiliar variety 

 with a long list of technical variety descriptions in order to make an identifica- 

 tion, a kej' is usually prepared by which varieties or groups of varieties can be 

 systematically eliminated from consideration. Such a key can be no more re- 

 liable than the characters used in making it. Since, as already pointed out, all 

 plant characters are more or less variable, no key can be perfect. It should always 

 be used in connection with good technical descriptions. Used with its limitations 

 and advantages in mind a good key can be a great help. The following key was 

 prepared with these points in mind. 



A Leaf margin serrulate 



B Leaf midrib pubescent on top only *1S Rancocas 



BB Leaf midrib pubescent on both sides 



C Tip leaves erect 20 Wareham 



CC Tip leaves not erect 9 Harding 



AA Leaf margin entire 



B Leaf midrib pubescent on both sides 



C Shoots pubescent . . ' 8 Grover 



CC Shoots not pubescent 1 Adams 



BB Leaf midrib not pubescent on both sides 



C Leaf length distinctly less than twice the width 



D Leaf midrib not pubescent 10 Jersey 



DD Leaf midrib pubescent or top 



E Leaves slightly waved and twisted 2 Atlantic 



EE Leaves neither waved nor twisted 

 F Petiole pubescent 



G Pockmarking of some leaves 19 Stanley 



GG No pockmarking 12 Katherine 



FF Petiole not pubescent 13 Pemberton 



CC Leaf length twice the width or nearly so 

 D Petiole pubescent 



E Some leaves reverse curved 14 Pioneer 



EE Leaves not reverse curved 



F Leaves ovate 6 Dixi 



FF Leaves narrow elliptic 4 Cabot 



DD Petiole not pubescent 



E Leaves reverse saucer-folded 17 Sam 



EE Leaves flat to broadly V-folded 

 F Leaves distinctly elliptic 



G Leaf margins not distinctly reflexed. ... 16 Rubel 



GG Leaf margins strongly reflexed 3 Burlington 



FF Leaves elliptic to ovate 11 June 



CCC Leaf length distinctly more than twice the width 



D Some leaves distinctly mottled and bullate 7 Dunfee 



DD Leaves not mottled and bullate 



E Petiole pubescent (on top) 21 Weymouth 



EE Petiole not pubescent 



F Leaves twisted 5 Concord 



FF Leaves not twisted 



G Leaf surface dull 1!* Scammell 



GG Leaf surface glossy 22 No. 73 



*See variety descriptions, pages 17-19. 



