3 16 
C0MP0S1TAE 
with 5 teeth at the end representing the petals, but is usually also 
given to those lipped forms where the lower lip is strap^shaped 
and ends in 3 teeth. Sta. 5, epipetalous with short filaments, 
alternating with the petals. Anthers introrse, cohering by their 
edges ( syngenesious ), forming a tube around the style (cf. Lobelia). 
Ovary inferior, of (2) cpls., with a simple style that forks at the end 
into two stigmas, an anterior and a posterior (see diagram). The 
construction of the style and stigma is of importance in the classifica- 
tion of the order. There is often a brush of hairs on the style below 
the stigmas. Only the inner (upper) surfaces of the stigmas are as a 
rule receptive to pollen. Ovary i-loc. with 1 erect, basal, anatropous 
ovule, which gives an exalbuminous seed with straight embryo, en- 
closed in the dry indehiscent pericarp. This fruit is usually termed 
an achene, but of course is, if one adheres strictly to the usual defini- 
tions, a pseudo-nut, as its pericarp is partly of axial nature, and there 
is more than one cpl. It is often crowned with a pappus (see 
below).’ 
Natural History of the Flower . Being massed together in heads, 
the individual firs, may be, and usually are, comparatively very small. 
By this means this advantage is gained that a single insect visitor 
may fertilise many firs, in a short time without having to fly from one 
to the other, while at the same time there is no loss of conspicuous- 
ness, and of course a considerable saving of corolla-material, &c. 
The various sex-distributions occurring in the order have been men- 
tioned above. Coming now to the mechanism of the individual fir., 
we find, throughout the order, the same type, the differences between 
the different genera being in slight and unimportant details. The 
mechanism itself is simple, but effective. Honey is secreted by a 
ring-shaped nectary round the base of the style, and is protected from 
rain and from short-lipped insects by the tube of the corolla. The 
depth of the tube varies within fairly wide limits, but is never so 
small as to permit the shortest-lipped insects to obtain the honey. 
As an order the C. all belong to Muller’s floral class B' (see p. 91), 
but there is considerable variety in the depth of tube &c., and 
therefore also in the composition of the group of visiting insects 
to each. Thus the long-tubed purple-flowered Centaureas &c. are 
mainly visited by bees and Lepidoptera, while the short-tubed yellow 
Leontodons or white Achilleas are visited mainly by flies (see Muller’s 
Fert. of Firs., or Ann. of Bot. June 1895). 
At the time when the fir. opens, the style, with its stigmas tightly 
closed against one another, is comparatively short, reaching up to, or 
projecting a small distance into, the anther tube. The pollen is shed 
into this and as the style grows it presses the pollen little by little 
out at the upper end of the tube where it will come into contact with 
visiting insects. At last the style itself emerges and the stigmas 
separate. The fir. is now in its female stage. Finally, in a great 
