COMPOSITAE 
3i5 
calices of the individual firs., viz. protection of the bud and of the 
young fruit. The firs, are arranged upon a common receptacle, 
— the enlarged end of the axis — which may be of various shapes, 
but is most frequently flat, slightly convex or even spindle-shaped. 
The shape and the surface-condition of the receptacle are characters 
of importance in the classification of the order. It may be smooth or 
hairy, &c. ; there may (Helianthus, &c.) or may not (Calendula, &c.) 
be, upon it, scaly bracts belonging to the individual firs. In Cynareae 
these bracts are divided so as to form numerous bristles. 
In the simplest case the firs, of a single head are all alike and £ , 
but there are many deviations from this type. The firs, may be all 
actinomorphic ( tubular ) or all zygomorphic ( ligulate ) ; see below. 
Very commonly however, as in the daisy or sunflower, there is a 
distinction into a disc of actinomorphic firs., and a marginal ray of 
zygomorphic firs. Or, as in Centaurea sp. the outer florets may 
be actinomorphic but different in size from the central ones. The 
number of ray-florets varies in different sp., but always according 
to definite rules (see p. 22). 
The distribution of sexes among the firs, of a head is another 
feature which varies much (for details see Hildebrand, Geschlechter- 
vertheilung bei den C. f or Muller, Fert. of Firs.). The most common 
case is gynomoncecism, the ray-florets being ? , the disc £ . This 
would appear to be a mere correlation due to exigencies of nutrition, 
and not an “adaptation” (see p. 25); it can hardly be looked upon 
as advantageous in the direction of cross-fertilisation, in view of the 
fact that in many sp. the ray-florets are rarely fertilised at all. It 
seems probable that the extra material in the large corolla is supplied 
at the expense of the androeceum. The very large ray-florets of 
Centaurea sp. and others are completely sterile (cf. Hydrangea, 
Viburnum, &c.). Other interesting sex-distributions are found in 
Tussilago, Petasites, &c. (y.z>.). 
The flower is fully epigynous, usually 5-merous. The calyx is 
absent in Ambrosia and its allies, Siegesbeckia, 
&c. ; in some cases it appears only as a slightly 
5-lobed rim upon the top of the inferior 
ovary (cf. Rubiaceae and Umbelliferae); usually, 
it takes the form of hairs or bristles — the pap- 
pus — and enlarges after fertilisation into a 
parachute (Dandelion) or into hooked bristles 
(Bidens) to aid in distribution (see below). 
Corolla (5), valvate in bud. It may be acti- 
nomorphic (tubular) or zygomorphic. Of the 
latter form there are two varieties, labiate 
(lipped) and ligulate (strap-shaped). The 
latter term, strictly speaking, should be applied 
to those corollas which are strap-shaped in form 
Floral Diagram of 
Composite fir. with pap- 
pus (after Eichler). The 
small outer lines repre- 
sent the pappus- bristles. 
