AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
190 
and the greatest modification is found in V. Schiedeana Less., ranging from 
Honduras to Vera Cruz, with involucral scales broadly dilated at the tip. 
The progressive specialization in structure, correlated with increasing dis¬ 
tance to the north, is here clearly shown. 
There now follow seven species-groups with 33 species, all West Indian, 
all clearly related, and all exhibiting a remarkable correlation between 
structure and distribution. 
The most primitive of these, from which the other six are directly or 
indirectly derived, is the Arborescentes, ranging from the Windward Islands 
to Jamaica. The wide range and primitive structure probably indicate an 
early arrival in the region. The most primitive species, V . icosantha DC., 
has stems bearing leaves of normal size to the apex and terminating in a 
single sessile head. At the base of this head the two primary cymes arise; 
they are straight, elongate, with prominent internodes, sparingly branched 
or simple, and bear numerous heads. The chief distinction in the inflo¬ 
rescence between it and the Graciles is the regular presence of paired primary 
cymes. In V. sericea L.C.Rich., of the Virgin Islands and Porto Rico, 
the cymes are shorter and more frequently branched. V. borinquensis 
Urban, of Porto Rico, has exceedingly flexuous, many-headed, freely 
branched cymes, the branches invariably arising at the base of a head. V. 
arborescens (L.) Sw., of Jamaica, has numerous frequently congested cymes 
and reduced bracteal leaves. V. permollis Gleason, of Jamaica, completes 
the group, with congested cymes and an unusual development of foliar pu¬ 
bescence. The general tendency of the group is toward the production of 
cyme-branches and supernumerary cymes, making a congested inflorescence 
in which the bracteal leaves are reduced. 
The Longifoliae, a group of three species, is related through V. longi- 
folia Pers., of the Lesser Antilles, to V. icosantha. Superficially the two 
species are much alike, but the inflorescence in the former shows a distinct 
difference. The primary cymes are short, compact, divergently spreading 
at an angle of 60-90°, crowded, bearing only 2-5 heads on short internodes 
with bracteal leaves considerably smaller than the heads. Secondary cymes 
arise just below the primary in the upper leaf axils. They are essentially 
leafless for the first 2-5 cm., and then bear toward the summit either the 
usual crowded heads or a terminal head subtended by two short cymes. 
This whole inflorescence terminates completely the growth of this portion 
of the stem, but during the next vegetative season new branches appear 
from the next lower axils in order, grow out at a divergent angle, soon 
surpass the old cymes of the previous season, and at the next blooming 
season bear their cymes in turn. The plant has therefore a method of 
continuing its vegetative growth beyond one season, and as a result reaches 
a considerably larger size. V. Shaferi Gleason, of Montserrat, is closely 
similar, and represents an island endemic. V. albicaidis Pers., of the Virgin 
Islands and Porto Rico, preserves the same inflorescence but differs in its 
obtuse or broadly rounded leaves. 
