n out of the anther tube, and finally the
stigmas spread and expose their receptive surface which has hitherto
been hidden, the two being pressed together. Thus the life history of
the flower falls into two stages, an earlier or male and a later or
female. This favours cross-pollination as compared with
self-pollination. In many cases there is a third stage, as in dandelion,
where the stigmas finally curl back so that they touch any pollen grains
which have been left on the style, thus ensuring self-pollination if
cross-pollination has not been effected.

The devices for distribution of the fruit are very varied. Frequently
there is a hairy or silky pappus forming a tuft of hairs, as in thistle
or coltsfoot, or a parachute-like structure as in dandelion; these
render the fruit sufficiently light to be carried by the wind. In
_Bidens_ the pappus consists of two or more stiff-barbed bristles which
cause the fruit to cling to the coats of animals. Occasionally, as in
sunflower or daisy, the fruits bear no special appendage and remain on
the head until jerked off.

[Illustration: FIG. 2.--Flowering shoot of Cornflower. 1. Disk-floret in
vertical section.]

Compositae are generally considered to represent the most highly
developed order of flowering plants. By the massing of the flowers in
heads great economy is effected in the material required for one flower,
as conspicuousness is ensured by the association; economy of time on the
part of the pollinating insect is also effected, as a large number of
flowers are visited at one time. The floral mechanism is both simple and
effective, favouring cross-pollination, but ensuring self-pollination
should that fail. The means of seed-distribution are also very
effective.

A few members of the order are of economic value, e.g. _Lactuca_
(lettuce; q.v.), _Cichorium_ (chicory; q.v.), _Cynara_ (artichoke and
cardoon; q.v.), _Helianthus_ (Jerusalem artichoke). Many are cultivated
as garden or greenhouse plants, such as _Solidago_ (golden rod),
_Ageratum_, Aster (q.v.) (Michaelmas daisy), _Helichrysum_
(everlasting), _Zinnia, Rudbeckia, Helianthus_ (sunflower), _Coreopsis_,
Dahlia (q.v.), _Tagetes_ (French and African marigold), _Gaillardia,
Achillea_ (yarrow), _Chrysanthemum, Pyrethrum_ (feverfew; now generally
included under _Chrysanthemum_), _Tanacetum_ (tansy), _Arnica,
Doronicum, Cineraria Calendula_ (common marigold) (fig. 1), _Echinops_
(globe thistle), _Centaurea_ (cornflowe