208 INDEFINITE INFLORESCENCES.—UMBEL. 
florets are fully expanded, those within them less so, and those 
in the centre in an unexpanded condition. Here therefore the 
order of expansion is towards the centre—that is, centripetally. 
The capitulum is the universal form of inflorescence in plants of 
the natural orders Composite and Dipsacaceze ; and is also found, 
more or less, in some orders allied to these. Capitula of a less 
marked character are also to be seen in other orders ; as in the 
species of Clover (Trifolium), and many Proteaceous plants ; 
in these, however, the involucre is always absent. 
The arrangement of the flowers in the Fig (fig. 406) and 
Dorstenia (fig. 407) also closely resembles that of an ordinary 
capitulum, and such arrangements are sometimes regarded as 
special varieties of the capitulum ; but the involucre is in these 
Fie. 428. 
\ 
\ 
\ 
SN ‘i 
Fig. 428. Capitulum of 
Seabious (Scabiosa). 
The outermost florets 
may be observed to be 
more expanded than 
the inner.— Fig. 429. 
Simple umbel of a 
species of Allium, 
inflorescences always absent, and the flowers are developed cen- 
trifugally, as in the glomerule (page 216), to which kind of in- 
florescence they therefore more properly belong. 
b. The Umbel.—When the primary axis is shortened, and 
gives off from its apex a number of secondary axes or pedicels of 
nearly equal length, each bearing a flower, and the whole ar- 
ranged like the ribs of an umbrella, an wmbel is formed (fig. 429), 
as in the Onion and Cowslip. When the secondary axes them- 
selves divide, and form tertiary axes, which are also arranged in 
an umbellate manner, a compound wmbel is produced. This is 
seen in the Carrot (jig. 398), the Fennel (jig. 430), and other 
allied plants, which are hence called wmbelliferous, and give the 
name to the natural order Umbelliferee. In the compound 
umbel (fig. 430), the primary umbel a is called the general wnbel, 
and the other umbels, b, b, b, formed by the divisions of this, 
