40 FIELD AND FOREST. 



Mossy-cup Oak from the north ; still it may be truly said that these 

 are the only valuable species not found in a native state within the 

 limits named. Besides being the characteristic tree of this region as 

 respects number and abundance the oak is here represented by an un- 

 usual number of species and varieties. 



From a somewhat thorough study of the genus in the vicinity of 

 Washington, I find that of the sixteen distinct species enumerated in 

 the fifth edition of Gray's Manual, as indigenous to the Northern 

 United States east of the Mississippi, eleven belong to our district, as 

 follows : Quercus alba, Q. obtusiloba, Q. bicolor, Q. frinus, Q. phel- 

 los, Q. imbricaria, Q. nigra, Q. falcata, Q. coccinea, Q. rubra, and 

 Q. palustris. 



Among the settled varieties of these we also find distinct examples 

 of Q. prinus, var. monticola, and var. accuminata, and of Q. coccinea, 

 var. tinctoria. 



In addition to these occur several anomalous forms, presumed to be 

 hybrids, which afford an especial interest. In no less than six of 

 these, after a careful comparison of the leaves and fruit and a close 

 study of their respective localities and of the species growing in the 

 immediate vicinity of each, the original species of whose joint paren- 

 tage they are the probable offspring, can be traced with a considerable 

 degree of certainty. 



A peculiar form of Q. alba, having leaves with short lobes and shal- 

 low sinuses directed much forward, as well as the veining, and thus 

 simulating those of Q. prinus, renders it quite probable that these 

 species have intercrossed. 



There are some forms of Q. bicolor whose unusually long, narrow 

 and elliptical leaves hint strongly at an affiliation with Q. prinus, var. 

 accuminata, while on the other hand certain trees belonging unques- 

 tionably to the last named variety, not only exhibit the whitened- 

 downy under surface of leaf characteristic of Q. bicolor, but also show 

 a tendency to reduce the number of primary veins to from 8 to lo, 

 thus affording additional proof of the ability of these forms to inter- 

 cross. 



Passing into the biennial fruited division, we observe this process of 

 hybridization still more distinctly manifest. 



Certain trees having some of their leaves almost entire, raise a strong 

 suspicion that Q. imbricaria has exerted an influence more or less 



