I9 8 AMERICAN JOURNAL OF BOTANY [Vol. 10, 



and V. interior are frequently intermediate in character. V. aborigina 

 Gleason, known so far only from the original collection in southeastern 

 Oklahoma, appears to be a giant form of V. Baldwini. It retains most of 

 the morphological characters of that species, but is much larger in all its 

 dimensions, with about twice as many flowers in each head. V. missurica 

 Raf., the last of the group, has the widest distribution of the four, ranging 

 from Texas, where it is not particularly common, north and east to Michi- 

 gan, and becoming exceedingly abundant in Iowa, Illinois, and Indiana. 

 It is characterized by larger, more compact inflorescence, fully differentiated 

 pappus, and regularly imbricated involucre. Many specimens from the 

 southern part of its range retain the sharply acute, relatively narrow invo- 

 lucral scales of V. interior, while those from farther east have fewer, broader, 

 and obtuse or apiculate scales. The species also occurs to a limited extent 

 and with slightly different structure along the Gulf Coast as far east as 



Alabama. 



The origin of two other western species is in doubt. V. Bolleana Sch.- 

 Bip., of northwestern Mexico, seems to bear no close relation to any other 

 known species. V. crinita Raf., of the Ozarkian region, is characterized by 

 filiform involucral scales, and may represent an extreme development from 

 the Interiores. 



The eastward migration along the coastal plain from Texas led to the 

 present development of seventeen species. They are not easily divided 

 into distinct species-groups, a feature possibly indicative of recent immi- 

 gration and evolution. The most primitive group is the Angustifoliae, 

 ranging from Louisiana east to the Atlantic, thence north to the Carolinas 

 and south into Florida and the Bahamas. The group retains the primitive 

 involucre, narrow leaves, and low stature of the Texanae, and the type 

 species of that group was originally described as a variety of V. angustifolia 

 Michx. Some of the species have an inflorescence approaching umbelliform 

 and rather suggestive of V. liatroides DC. or other species of northern 

 Mexico. V. angustifolia has the widest distribution, almost coextensive 

 with that of the group. The other four, each of restricted distribution and 

 lacking the acuminate scales of the simpler species, seem to represent recent 

 evolutionary developments. Of these, V. Blodgettii Small, in southern 

 Florida, marks the re-entrance of the group into the tropics, and leads to the 

 closely related V. insularis Gleason of the nearby Bahamas. 



The group Pulchellae is obviously closely related to the Angustifoliae, as 

 shown by narrow leaves and general vegetative habit, but differs in the 

 absence of resin glands on the achenes and in the prolongation of the in- 

 volucral scales into filiform appendages. The three species, V. pulchella 

 Small, V. recurva Gleason, and V. scaberrima Nutt., are all of limited dis- 

 tribution in the coastal plain of Georgia and the Carolinas. 



The species-group Glaucae lies generally to the north of the Angusti- 

 foliae and has probably been derived from it. Here the heads are larger, 



