Hill: Celtis pumila Pursh 499 



Arizona, coll. Marcus E. Jones (with mature fruit) and from 

 river bottoms, Oregon, coll. Drake and Dixon, Portland, Oregon. 



Mississippi 



Mississippi 



pumila 



den talis L. and C. Mississippi^ nsis Bosc. Its fruit characters, es- 

 pecially as seen in the nutlet, bring it much closer to the latter and 

 to C. reticulata Torr. (or C. Mississippiensis var. reticulata Sargent, 

 if considered a variety). It very often has the entire leaves of C. 

 Mississippiensis. The leaves of this species are narrower and rel- 

 atively longer, but when short and broad approach those of C. 

 pumila. Sometimes the leaves of C. occidentalis resemble those of 

 C pumila if the latter has them rather closely and evenly serrate 

 on one or both margins, as in the specimen of W. M. Canby from 

 Delaware. It is also seen in examples of the common hackberry 

 from the Desplaines River in which the leaves are considerably 

 thickened at fruiting time like those of C. punnla. The leaves of 

 Celtis occidentalis are prevailingly much longer acuminate, thinner, 

 though with a tendency to thicken in autumn, frequently scabrous, 

 more apt to have a cordate base or one less oblique, and often be- 

 come much larger. Being a tree, it has a trunk roughened by the 

 peculiar bark of narrow, prominent, broken ridges so character- 

 istic of the hackberry. The shrubby habit and peculiar mode of 

 branching of C. pumila (that of C. occidentalis usually being as- 

 cending or making a sharper angle with the support) are features 

 that at once strike the eye. The smaller winter buds, the flower- 

 ing season from 10 to 15 days later than that of C. occidentalis, 

 greener flowers with longer stigmas, commonly more hairy and 

 more nearly entire sepals, shorter filaments, smaller, globular, 

 lighter colored fruit, and especially the smaller globose nutlet 

 with a white reticulated pitted surface, seed covered with a white 

 membrane (that of C. occidentalis being light brown or dark 

 brown near the black spot of the chalaza), are the most distinctive 

 characters of C. pumila as compared with C. occidentalis. 



A comparison of the nutlets of four species, enlarged 8 diam- 

 eters, is given in connection with the text figures 1-4. 



