THE CLASSIFICATION OF PLUMS 187 



IX. AMERICANA GROUP (Prunus americana]. Tree 

 rather small, but in extreme cases reaching a height of 

 of fifteen to twenty-five feet; short jointed, dark col- 

 ored, hard wood, thorny; leaves large, coarse, rough, 

 more or less pubescent, especially underneath, 

 coarsely double-serrate; petioles seldom glandular; 

 fruit mostly dull red, occasionally yellow; flesh yellow, 

 soft, juicy; skin tough, frequently astringent. Native 

 to the Mississippi Valley generally. Represented by 

 hundreds of varieties, which, however, are very simi- 

 lar to one another. Typical named varieties are 

 Hawkeye, De Soto, Stoddard. 



X. NIGRA GROUP (Prunus americana nigra). Some- 

 what like the foregoing group, but bark darker col- 

 ored; leaves broader and more obtusely pointed, less 

 conspicuously double serrate; petioles always glan- 

 dular; fruit dark colored, compressed. Native to 

 this continent; general range from Ontario and New 

 York, north and east. Cheney and Aitkin are repre- 

 sentative varieties. 



XI. VAN BUREN TYPE. Certain plums, resembling 

 Prunus americana in general appearance, have leaves 

 and young shoots strongly pubescent. These varie- 

 ties seem to occur in nature most frequently in the 

 southwestern states Arkansas, Oklahoma, and Texas. 

 This variation has been recognized botanically in the 

 name Prunus americana mollis. Varieties in cultiva- 

 tion which show this characteristic pubescence are 

 Van Buren and Wolf. 



XII. MINER TYPE (Prunus americana mineri). 

 Closely related to Prunus americana; differing chiefly 

 in having leaves a trifle smoother, not so coarsely and 



