1G8 TRELEASE— CLASSIFICATION OF BLACK OAKS. [April 19, 



translator^ and of Professor Sargent,*' making the ovules appear to 

 be basal in the black oaks ; and on puzzling facts as well as observa- 

 tions on the dwarf live oaks, particularly 0. Emoryi which Engel- 

 mann' and Greene* have treated as a black oak on its general assem- 

 blage of characters, and Sargent^ (as did Engelmann^° at first) 

 places with the white oaks because of its basal ovules. 



Without attempting a critical analysis of hybrids, segregates and 

 aberrants, the present communication ofifers what appears to be a 

 natural grouping of our black oaks, which have been arranged in 

 floras and monographs usually and diversely in sequence dictated by 

 convenience of foliage contrast — that is, descriptively rather than 

 taxonomically. 



The classification here proposed was adopted some months since 

 when the oaks growing about St. Louis were selected to illustrate to 

 a university class the synthesis of generic concepts out of specific 

 characters. This local flora is fairly rich in representation of Quercus, 

 for its dozen species constitute about two-thirds of those of Missouri, 

 half of those of the northeastern states, a fourth of those of the 

 United States, and a twentieth of those of the world. For this rea- 

 son it has been comparatively easy to extend the conclusions based 

 on the local species so as to embrace all of those occurring east of 

 the great plains — which are evidently of a common stock. The few 

 species occurring between the continental divide and the desert, and 

 the few found west of this natural barrier, appear to represent 

 groups more properly coordinated with the entire assemblage of 

 eastern species than with the sets into which this is divided. In 

 them, perhaps, is to be found the key to an understanding of the 

 history of the genus as it is now represented in North America. 



Not many words are needed to indicate the striking collective dif- 

 ferences in bud and fruit between the three groups, black oaks, scarlet 

 oaks and swamp oaks of the eastern states, as pictured in the accom- 



°A. de CandoUe, Trans. Edinburgh Bot. Soc, 7: 440. 1863. 



" Sargent, " Manual, Trees of N. A.," 227. 1905. 



' Engelmann, /. c, 388, 394. 



' Greene, " 111. of W. A. Oaks," 45. 1889. 



'Sargent, /. c, 230, 286. 



'" Engelmann, /. c, 381-2. 



