Apr., 1923] 
GLEASON — VERNONIA IN NORTH AMERICA 
195 
of the stem, and new vegetative parts appear only from the perennial base 
of the plant. In the fifth and last stage, only a few terminal and subtermi¬ 
nal heads retain the umbellate arrangement, while from the upper stem 
axils similar clusters arise, producing a broad, flat-topped or hemispheric 
cluster with all the heads peduncled. These five stages are shown diagram- 
matically in figure 2. 
Fig. 2. Modifications of the inflorescence in the bractless Vernoniae of North America 
A. Stage 1, Vernonia scorpioides, lateral branch with two terminal cymes. B. Stage 2, 
canescens, lateral portion of the inflorescence. C. Stage 3, havanensis, portion of a terminal 
inflorescence. D. Stage 4, Karvinskiana, terminal inflorescence, with a few primary branches 
omitted. E. Stage 5, texana , complete terminal inflorescence. All figures diagrammatic 
as to position of branches or cymes, but accurate as to character of branching and pro¬ 
portion. 
Other evidences of evolution appear within the last two stages, leading 
to the segregation of several species-groups. 
The five stages are again well correlated with their geographical dis¬ 
tribution. The first occurs in South America and is represented in our 
region by a single species of St. Vincent, V. pallescens Gleason, and by two 
which extend across the Isthmus of Panama into southern Central America, 
V. scorpioides (Lam.) Pers. and V. brachiata Benth. The second includes 
