CORNELL UNIVERSITY EXPERIMENT STATION BULLETINS. 215 



hardest knot in American pomology. The botanical status of the native 

 plums is equally unsatisfactory, and the group is one of the most inextri- 

 cably confused of any one of equal e'xtent in our whole flora. There are a 

 few botanical features which are reliable in the characterization of the 

 species, and the specimens which are preserved in the leading herbaria are 

 few and unsatisfactory. There is probably no group of American plants 

 in which the characters of growing trees and fresh fruits are more essential 

 in the distinguishing of species than in these plums. Yet there are the 

 most remarkable variations in habit of tree, seasons of blooming and ripen- 

 ing, size, flavor and texture of fruit, and characters of stone, even among 

 varieties coming presumably from the same species. Fully half of the 

 varieties now in cultivation were picked up in woods and copses and trans- 

 ferred to the orchard, and the variations between these varieties are fully 

 as great as between those of known or garden origin. There is evidence 

 that hybridity is responsible for some of the variation of cultivated forms, 

 but whether it takes place in nature is wholly a matter of conjecture. It 

 is an unsafe principle to invoke the aid of hybridity, upon purely specula- 

 tive grounds, to explain doubtful points; and I have therefore referred 

 doubtful forms directly to the most closely allied species or type, so far as 

 possible, leaving speculations as to their true affinities to future students. 

 The native plums can be commended with confidence to any one who 

 desires to study contemporary evolution. 



Jn the following study, which has now extended through six years, I have 

 had the co-operation of many botanists and horticulturists. I am under 

 especial obligations to all those whose names are mentioned in this paper, 

 particularly to J. W. Kere, Denton, Maryland, and T. V. Munson, Denison, 

 Texas. Without the aid given by these last two persons the preparation 

 of this monograph would have been impossible. Mr. Kerb probably has 

 the largest growing collection of native plums in existence, and I have had 

 the advantage of a personal inspection of his orchards in the fruit season. 

 I have had access to the herbarium collections at Harvard university, Colum- 

 bia college, department of agriculture, and the Engelmann collection of the 

 Missouri Ijotanical gardens. Several botanists have favored me with 

 material, especially Dr. C. E. Bessey, university of Nebraska, Dr. T. C. 

 Porter, Easton, Penn., and H. N. Patterson, Oquawka, Illinois. And I 

 have enjoyed the great advantage of having had the advice of Professor C. 

 S. Sargent, who has critically examined some two or three hundred of 

 our specimens. In the following descriptions, those varieties marked C 

 are in cultivation at Cornell. 



§ 1. Classification of the Cultivated Native Plums. 



A. The Americana Group. {Prunus Americana, Marshall, Arbustrum 

 Americanum, 111, [1785]). 



To this type belong the hardy, strong-growing varieties which have come 

 from the northwest, and which are characterized by a firm, meaty, usually 

 compressed, dull-colored late fruit, with thick and usually very tough, 

 glaucous skin, and large, more or less flattened stone which is often nearly 

 or quite free, and by large obovate, thick, veiny, jagged, dull leaves. 

 Primus Americana is generally distributed throughout the northern states 

 from western New England to Kansas and Nebraska, and to the mount- 

 ains of Montana and Colorado, in the middle longitudes reat.-hing as far 



