Apr., 1923] 
GLEASON — VERNONIA IN NORTH AMERICA 
189 
bescence of the cauline leaves and differ from them chiefly in size. The head 
is pediceled if separated from the bract by an obvious internode, and the 
inflorescence is then a scorpioid raceme. If this internode is reduced, the 
head is sessile and the cluster becomes a scorpioid spike. The clusters may 
be straight or flexuous, long or short, crowded or loose, with heads ranging 
from 2 to 25 in number. As a result of the straightening of the sympodial 
axis, the heads appear lateral and are usually placed about 90° around the 
axis from the bracteal leaf. 
The leafy scorpioid cyme is found in 57 species, ranging throughout the 
West Indies and on the continent extending north into southern Mexico. 
Species with leafless cymes, 63 in number, occur commonly on the continent 
from Panama to New England. From this region four have crossed the 
narrow gulf east of Yucatan and entered Cuba; one has reached the Bahamas 
from Florida; one is endemic to St. Vincent, and another reaches Trinidad 
and the neighboring islands. In general, the distribution of the latter group 
is continental, of the former Antillean. 
Perhaps the simplest type of the primitive leafy inflorescence is found 
in the species-group Graciles, in which the cymes are stemlike and quite 
undifferentiated from the truly vegetative portion of the stem, with 
bracteal leaves closely resembling the cauline in size and shape. Species 
of this group are almost entirely South American, ranging, according to 
Ekman, from Colombia to eastern Brazil. One species only, V. gracilis 
H. B. K. var. tomentosa Ekman, of Bequia, occurs in our range. 
A second group, with almost equally simple inflorescence, composed 
of long, irregular, branching cymes, with long internodes and leaflike bracts, 
is the Argyropappae, of tropical South America, Central America, and 
southern Mexico. The South American origin of the group may be assumed. 
From there, V. remotiflora Rich, has been introduced into St. Thomas; 
V. acilepis Benth. is endemic to Costa Rica, and V. argyropappa. Buek 
extends from Peru to Mexico. Two offshoots of the latter have arisen in 
Mexico, V. hirsutivena Gleason in Yucatan and V. ctenopliora Gleason in 
Campeche, differing in minor structural details. 
It will be observed that these two groups, simplest in structure, are 
distributed primarily in South America and that only a part of their species 
reach North America, although among these are three endemic species and 
one endemic variety. 
A third group of similar primitive structure as to inflorescence is the 
Schiedeanae, of Central America and southern Mexico. While its members 
differ sharply from the preceding group in their large heads, the peculiar 
development and specialization of the involucral scales, and the absence 
of foliar resin dots, they retain the simple cymes and broad, heavy leaves, 
and may possibly be derived from it. V. vernicosa Klatt, with narrow 
acuminate scales, appears to be the simplest and is endemic to Costa Rica. 
V. Seemanniana Steetz follows in Costa Rica, with broad, obtuse scales, 
