188 THE EVOLUTION OF OUR NATIVE FRUITS 



in Maryland; 12, Weaver (P. nigra), grown in Mary- 

 land ; 13, Weaver, grown in Minnesota ; 14, Weaver, 

 grown in Texas. 



To give the reader an opportunity to compare this 

 interesting variation in plum stones with like varia- 

 tion in another and foreign species, I insert a picture 

 (Fig. 27) of stones of the myrobalan plum (Primus 

 cerasifera) selected from an imported commercial 

 sample. (See discussion beginning on page 208.) 



The early flowering of some trees of this Primus 

 Americana stock is a most conspicuous character, but 

 I do not see that it should excite any more interest 

 than the very early maturing of fruit on some trees ; 

 nor do I see that an occasional large -flowered form 

 is any more worthy of being accorded specific rank 

 than a large -fruited form. These are all probably 

 individual variations, and likely have no close rela- 

 tion to the genetic history of the species. 



I am obliged, therefore, to unite Prunus nigra 

 with P. Americana. This I regret the more because 

 it is undoubtedly true that there are two or more well 

 marked wild varieties passing as P. Americana, and 

 growing together in the East. One type is a twiggj', 

 virgate grower, with large and mostly earlier flowers ; 

 another is a stout and stiff grower, with small flowers. 

 So far as I have been able to determine, the fruits 

 and stones of these two forms, save possibly in time 

 of ripening, are not characteristically distinct. These 

 forms are certainly common in central New York and 

 in Michigan. It is a question, however, if the habit 

 of growth is not largely determined by the soil, posi- 

 tion, or other circumstances in which the trees grow. 

 At all events, these differences are not more marked 



