123 
Origin and Development of the Compositce. 
genus, Centanrea, has undergone various modifications; spines or 
more or less elaborate appendages are frequently present at the 
apices of the bracts. The pericline is in two or more rows, and 
usually passes gradually into the calyculus. A similar involucre 
without the elaborate appendages is the rule in the Cynareae. The 
only difference in the sub-tribes is the occurrence of a more or less 
foliaceous calyculus in two or three genera of the Centaureinae. 
Mutisiece. In the Barnadesiinae, Onoseridinse and Gochnatiinae 
the involucre is multiseriate without exception, This is interesting 
when the involucre of the Nassauviinae is considered; there only 
three small genera are multiseriate, the others varying from five 
or six bracts to a few rows. Perczia has two to many rows, the 
pericline being uniseriate and the calyculus frequently foliaceous. 
In Trixis the pericline is composed of from five to ten bracts in 
one row, and the calyculus is usually a few leaves, sometimes small, 
sometimes larger and foliaceous, rarely more numerous and in 
several rows. This is exactly the condition in Senecio (cp. Chap. V, 
Sect. D). In Nassauvia, where the cauline leaves are reduced and 
crowded they pass very gradually into the calyculus, cp. Bryomorplie 
and Eriotlirix. 
Vernoniece. The involucre is multiseriate as a rule, reduced 
to a few bracts in Corymb ium , Rolandra and Spiracantha , and 
pauciseriate in a few other genera. Vernonia and two or three 
other genera of the Vernoniinae have the calyculus occasionally 
foliaceous. 
Astcrece. The involucre is frequently multiseriate, but in the 
Homochrominae an uniseriate pericline with a more or less foliaceous 
or reduced calyculus occurs in a number of genera and it is the rule 
in the Bellidinae and Grangeinae. This primitive involucre is the 
commonest form in the Conyzinae and Baccharidinae, but in both 
these tribes it is occasionally multiseriate. The Heterochrominae is 
very similar to the Homochrominae with even a larger proportion of 
genera showing the primitive involucre. The chief genera, however, 
are all multiseriate, except Erigeron and some species of Felicia 
which are biseriate. 
Eupatoriece. The involucre in Eupatorieae varies from one to 
many rows, with the calyculus small or equalling the pericline in 
the size of the leaves. Mikania is distinguished from Eupatorium 
by its pericline of four bracts with or without a few membered 
calyculus. The other genera vary from uniseriate ( Stevia) and 
hi- to triseriate (Ageratmn) to pauciseriate ( Alo?nia ). The smaller 
genera vary within a similar range. In the Piqueriinae, with the 
