Apr., 1923] GLEASON VERNONIA IN NORTH AMERICA 199 



the pappus is tawny or almost white, and the involucral scales are long- 

 acuminate or almost filiform. The leaves are large in proportion to the 

 height of the stem, and the greatest expanse of foliar surface is toward the 

 base of the stem. While this feature is apparent in V. glauca (L.) Willd., 

 an Alleghenian species ranging northward to Pennsylvania, it is still further 

 developed in V. acaiilis (Walt.) Gleason and V. georgiana Bartlett, two 

 coastal plain species with distinctly basal leaves. 



Two other species with prolonged filiform scales constitute the group 

 Noveboracenses. V. noveboracensis (L.) Michx. has attained a wide dis- 

 tribution over the Piedmont region of the eastern states from Mississippi 

 to Massachusetts, occasionally invading the coastal plain also. There it has 

 given rise to a localized species, V. Harperi Gleason, characterized by larger 

 heads with more numerous flowers. 



V. gigantea (Walt.) Britton is closely related to V. concinna Gleason, 

 of the Angustifoliae, and like that species is confined to the southeastern 

 portion of the coastal plain. 



The last species-group of the southeastern states is the Altissimae. V. 

 ovalijolia T. & G. is a variable species of the southeastern coastal plain, and 

 appears to be the most primitive species of the group in their evolution 

 from the Angustifoliae. Although some of its variants approach V. con- 

 cinna, it is generally distinguished by the broader, regularly imbricated 

 involucre and the broad leaves. V. flaccidifolia Small is a well-marked 

 species of the southern Appalachian region. V. altissima Nutt., the last 

 species of the group, has a wide distribution from Georgia and Alabama 

 north and west to New York and Missouri. Typical forms of the species 

 avoid the coastal plain and are characteristic of the woodlands of the central 

 states, but the variety laxa Gleason occurs along the Gulf Coast. In its 

 western extension V. altissima comes in contact with several species of the 

 western migration route, and many intermediate forms occur which are 

 probably to be considered as hybrids. 



Considering the 35 species with paniculate inflorescence as a whole, we 

 see that the species with primitive involucre invariably lie far to the south 

 or southwest, and that those with the broadest and most obtuse scales, as 

 well as those with the most filiform scales, lie always well to the north or 

 northeast. It is also worthy of note that only seven of the 35 have attained 

 a wide distribution, while the other 28 occupy small or localized ranges. 

 These seven are V. fasciculata Michx., V. interior Small, V.missurica Raf., 

 V. angustijolia Michx., V. glauca (L.) Willd., V. noveboracensis (L.) Michx., 

 and V. altissima Nutt., representing six species-groups. This fact alone 

 may indicate the comparatively recent immigration and incomplete evo- 

 lution of the genus in the northern portion of its range. 



The general relations of the 63 species of the genus in which the bracteal 

 leaves are suppressed is exhibited in a diagram (fig. 3). 



In the evolution of the genus in North America, no general plan or 



