GENUS PTELEA IN THE WESTERS AM) Sol 

 WESTERN UNITED STATES AND MEXICO. 



By Ej >\\ \i;i> 1.. < ; reene. 



INTRODUCTION. 



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

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

 been long in need of taxonomic investigation. In the days of George 

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

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

 and Canada to the sources of tin 4 Mississippi, thence southward over 

 the whole country 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 River 

 and the Pacific Ocean and including the whole of Mexico were credited 

 three species all recognized as typically Mexican, but believed to 

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

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

 since it was given out that we have in all North America north o^i 

 Mexico only two species and two varieties of Ptelea. 



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

 ognize that such a range as has been accorded to Bentham's middle 

 Mexican P. angustifolia is impossible 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 <>n the our 

 hand and Arizona and northern California on the other. 



It was long since due that the investigation of this genus a- existing 

 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 rich in 

 species of many another genus, abound in Pteleas, and -<• d<> Mexican 

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



Syn tptical Flora of North America, volume l. part l. pp. 372, •"•7.">. 1897. 



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