F" 



1' -'^- 



^ - 



TJIE GENUS PTELEA B THE ^VESTERS AND SOUTH- 



AVESTEKN 



STATES AND MEXICO. 



By Ejjward L. Greene. 



INTRODUCTION. 



This genus, in so far ns known exclusively North American, and in 

 my view of it somewhat anomalous and of not very certain affinity, has 

 been long- in need of taxouutnic investigation. In the days of George 

 Bentham and Asa Gray it was received as consisting of about iivc 

 species; one of them supposed to range all the way from New England 

 and Canada to the sources of the Mississippi, thence southward over 

 the whole comitry even to the shores of the Gulf of Mexico. A 

 second Ptelea was recognized , as local in Florida, while to all those 

 empires of territory lying westward between the Mississippi liiver 

 and the Pacilic Ocean and including the whole of ]\Icxico were credited 

 three species— all recognized as typically Mexican, but believed to 

 include all the Ptelea of Texas, of Califonua, and of all the vast 

 regions lying between thost; States. It is, indeed, less than ten years 

 since it was given out that we have in all North America north of 

 Mexico only tw^o species and two varieties of I*telea.« 



But in this first decade of the twentieth century everyone will rec- 

 ognize that such a rangi" as has been accorded to Bcntham's middle 



[A 



at least, to any mind having an 



understanding of all those extremes of diversity as to soil, climate, 

 altitude, and other potently influential conditions which exist between 

 southern Mexico and such regions as Texas and Oklahoma on the one 

 hand and Arizona and northern California on the other. 



]t was long since due that the investigation of tliis o-cnus as existing 



^^ ^^j y^ 



in the West and Southwest should be taken in hand. The center 

 of distribution for Ptelea lies somewhere in that direction. The 

 uncounted canyons cutting into the great Mexican plateau, so i-ich in 

 apecies of many another genus, abound in Pteleas, and so do Mexican 

 mountains everywhere. The like is as true of perhaps a hundred 



« Synoptical Flora of Xortli America, voluine 1, part 1, i)p. 372, 373. 1897. 



49 



