VALUE OF CHARACTERS. 367 
mon receptacle, within an involucre of several, often very many, 
rarely only two or three, closely packed bracts, which act more 
or less the part of the suppressed calyces in protecting the buds 
or the young fruits. Notwithstanding the special names given 
to these organs by various synantherologists, there is nothing to 
distinguish them from the corresponding organs in divers genera 
of Dipsacew, Umbelliferze, Cornaees, Myrtaceæ (Darwinia), Pro- 
teacex, Thy melec, and many others—nothing whatever except their 
constancy. In order correctly to understand the minor modifiea- 
tions to which these organs are subject, it is necessary to keep 
their homology in view ; and therefore it is that we have thought 
it better to retain the intelligible terminology of involucral bracts 
and receptacle, than to encumber it with such special terms as 
periclinium, phyllaries, clinanthium, &c., which only serve to give 
unnecessary trouble and convey false notions. 
The capitulum characterized by the involucre exists throughout 
the order; the involuere may in some compact compound inflores- 
cences be reduced to two or three bracts only, never, I believe, 
to a single one, even when uniflorous. The number (taken gene- 
rally within certain limits, rarely as absolutely precise) and 
arrangement of the bracts, their general form and consistency, and 
the general form the involucre itself or the capitulum (including 
the florets) assumes, afford generic characters in most cases excel- 
lent from their constancy, although, from their ready perceptibility 
and the aspect they give to the plant, they are apt to be too hastily 
observed and too implicitly relied upon. They are also far from 
absolute as tribual characters, although they may give good general 
indications. Thus the single row of inner equal erect involucral 
bracts, with or without much smaller or differently shaped or much 
looser outer ones, so common in Senecionidex, Helenioidew, and: 
Helianthoidew, are seldom, if ever, to be met with in Vernoniacesm, 
Eupatoriacex, Asteroides, Inuloidex, Anthemidex, Arctotidex, or 
Cynaroides. The ovoid or globular involucre with many rows of 
closely imbricate bracts is chiefly characteristic of Vernoniacerm, 
Cynaroidez, the subtribe Gorteriez of Arctotidee, a portion of 
Mutisiacex, and exists only in isolated genera in other tribes. The 
broadly hemispherical involucre with scarious-tipped or bordered 
inner bracts is general in Anthemidez, in the subtribe Euarctotex 
of Arctotidez, and in some Asteroides. Involucres, however, are 
sometimes deceptive, and precisely the same forms may be occa- 
sionally met with in two genera belonging to widely distant tribes, 
LINN. JOURN.—BOTANY, VOL. XIII. 2 E 
