52 CONTRIBUTIONS PROM THE NATIONAL HERBARIUM. 



it- winged margin, the seed-bearing body is central in some and vari- 

 ously eccentric in perhaps the greater number. This body of the 

 fruit, in it^ germinal stage in the flower that is, as an ovary is 

 raised onagynophore or stipe, which stipe, lengthening afterwards 

 w itb the gro\* i h of the wing in which it is merged, yet appears «>n the 

 surface of the wing below the body, just as the lengthened style is 

 manifesl as a Line running along the surface of the wing above the 

 body. I have expressed the centricity of the body by the phrase, 

 u style and stipe equal," its eccentricity in the direction of the base by 

 "style longer than the stipe,' 9 its nearer approach to summit a rare 

 condition -by "style shorter than the stipe." 



Bach one of the three natural groups of Ptelea here outlined has its 

 own geographical limits, and nothing in this study has more deeply 

 interested the investigator than the geographic distribution of the 

 groups. 



The principal one of the three that is. the group richest in species 

 and of most extended and varied range, the group with chestnut-brown 

 twigs and prevailingly glaucescent or bluish-green foliage is dis- 

 persed throughout at least middle and northern Mexico, as well as 

 adjacent southern Arizona. New Mexico, and Texas, thence northward 

 along the Mississippi to the Great Lakes, and every where eastward to 

 the Atlantic. 



A second group, that with twigs almost white and foliage yellow 

 green, forms a belt which runs eastward from northwestern Arizona 

 alone- the Grand Canyon of the Colorado, there and in southern Utah 

 forming a curious sort of boundary to the distribution of Ptelea north- 

 ward in that part of the country, tin 1 belt reaching iN eastern limit in 

 the canyon of the Arkansas in southern Colorado, from which point, 

 and still as a narrow belt, it runs down the Rio Grande to the neigh- 

 borhood of El Paso, Texas ; the belt in this part of its course not limit- 

 ing hut intersecting the great main division of the genus. 



The third group, that with cinnamon-colored twigs, a quite peculiar 

 hue and venation of foliage, and narrow-winged or even wingless 

 samaras, extend- in also a narrow belt, running northward and south- 

 ward west of the crest of the Sierra Nevada, between northern Cali- 

 fornia and at least the middle of the Lower California peninsula. 



Of the fifty-nine species here defined, not quite all arc new. t\\ <> <>r 

 three of them having been indicated somewhat recently by Dr. Small 

 and Mr. Heller, these belonging to the Texan district. 



Among the new ones are several of verj T recent detection in Mexico, 

 having come to hand only after this paper was nearing completion. 

 One of these was distributed by Mr. Pringle under tin 4 name Dr. 

 Rose had assigned it. The others Dr. Rose had himself collected 



and determined to he new. He has chosen that these should all he 



incorporated into this monograph, rather than give them separate 

 place am one his own miscellanies of Mexican botam . 



