Origin and Development o / the Composite. i 15 
essential characters of all genera, and is also used in the classi¬ 
fication of species within various genera, such as Pteronia (9), 
Centaurea and Liabum. 
Cassini (I, 18, Tome I, pp. 255-260) distinguished between the 
inner involucral bracts, which are usually more or less membraneous, 
and the outer involucral bracts, which may be very small and 
rather irregularly arranged or large and closely similar to cauline 
leaves. He named the collection of inner bracts the “ pdricline,” 
and the outer bracts when foliaceous the “ involucre.” Where the 
outer bracts are small this author considered that a “ pericline ” 
accompanied by bracteoles is present. In addition he described 
the variation in the form of the pericline and involucre at some 
length, giving the technical terms used in describing the appendages, 
margins, etc. 
Bentham (I, 7) considered this distinction of pericline and 
involucre to be misleading, and adopted the general term M involucre.” 
This practice has been followed very generally, the difficulty 
of the cases with foliaceous outer bracts which pass more or less 
gradually into cauline leaves being met by describing the involucre 
as duplex. Bentham also discussed the taxonomic value of the 
involucre, pointing out that this structure may give useful indica¬ 
tions of tribal affinities, but must be used with caution on account 
of its variability even in related genera. 
Morphology. Cassini ( loc. cit.) considered that the members 
of the pericline were the rudiments of petioles with flowers 
developed in the axils of all, if uniseriate, or with flowers aborted 
in the axils of the outer rows, if multiseriate. The members of the 
“ involucre ” he homologised with cauline leaves. The leaf base 
nature of the periclinal bracts is confirmed by Church (3). 
Bentham (op. cit. p. 367) apparently considered all the involucral 
members homologous with the flower-bearing, inner bracts. The 
bract-like nature of these inner members is confirmed by various 
abnormalities, such as that recorded by Offner (IV, 65 and see also 
descriptions of proliferations by Masters, IV, 52, and Worsdell, IV, 
97), and by Church’s observations (see Chap. VIII, B). The spines 
of the anomalous genus, Xanthium, were described by Baillon (V, 
3) as involucral bracts. 
The morphology of the outer involucral members has never 
been seriously considered, with the exception of Cassini’s few 
remarks, which have been neglected by most synantherologists. 
Blake (2) and others, however, have noted the similarity of these 
so-called bracts to reduced cauline leaves. 
