Manual of the New Zealand Flora.
[Introduction to Order XXXVIII. CompositÆ.]
Herbs, shrubs, or small trees. Leaves alternate, rarely opposite or whorled; stipules wanting. Inflorescence composed of one or many flower-heads (capitula), each consisting of numerous minute flowers (florets) sessile and densely packed on the enlarged tip of the flower-stalk (receptacle), surrounded by an involucre of whorled bracts and resembling a single flower. Heads either solitary and terminal (rarely axillary) or arranged, in corymbose cymes or panicles, sometimes contracted into clusters or even compound heads. Involucre of few or many bracts (scales of the involucre) arranged in one or several rows. Receptacle either naked (no bracteoles mixed with the florets) or with bracteoles in the shape of chaffy scales or bristles (palece) placed, at the outside of most or all of the florets, sometimes with the surface pitted or honeycombed. Florets many or few (very rarely 1), either all of one kind as regards sex, when the heads are said to be homogamous, or of more than one kind, when they are called heterogamous. The homogamous heads either have all their florets tubular and hermaphrodite (discoid) or all ligulate and hermaphrodite (liguliflorous). The heterogamous heads frequently have the central florets tubular and hermaphrodite or male, and the outer ones ligulate and female or neuter. The heads are then said to be radiate. The tubular florets in the centre are called florets of the disc, or simply disc-florets; the ligulate ones florets of the ray, or ray-florets. Heterogamous page 268heads are also discoid when the marginal female florets have tubular-corollas instead of ligulate. Calyx superior, adnate to the ovary and hardly to be distinguished from it; limb either wanting or composed of scales, bristles, or hairs, and then called pappus. Corolla gamopetalous, superior, either tubular or campanulate with 4–5 valvate lobes, or ligulate with the lobes cohering into a strap-shaped lamina which spreads to one side. Stamens 4–5, inserted on the tube of the corolla and alternate with its lobes; filaments usually free; anthers united into a sheath surrounding the style, cells sometimes produced at the base into bristle-like points or tails. Ovary inferior, 1-celled; style slender, 2-fid, branches short or long, linear, usually semi-terete, furnished with variously placed and arranged collecting-hairs for sweeping the pollen from the anther-cells, margins stigmatic; ovule solitary, erect, anatropous. Fruit a small dry seed-like nut called an achene, either crowned by the persistent pappus or naked. Seed erect, with a membranous testa;. albumen wanting; embryo straight, radicle short, inferior.
A vast order, by far the largest of flowering plants, comprising about 800 genera and 10000 species. It is found in every part of the world, from the-equator to the limits of phænogamic vegetation in the arctic and antarctic regions, and is equally plentiful in lowland districts and in mountainous or alpine situations. In New Zealand it constitutes rather more than one-seventh of the total number of flowering plants, a-somewhat large proportion, the ratio of the whole order to the flowering plants of the world being generally estimated at about one-tenth. Although so numerous in species, the order is far from being proportionately important from an economic point of view. Edible-species are singularly few, the chief being the Jerusalem and common artichoke, lettuce, and chicory. Oils are yielded by the sunflower and by Madia sativa. The chief medicinal plants are arnica, wormwood, and camomile. Many ornamental species are cultivated in gardens, as the various kinds of chrysanthemums, dahlias, cinerarias, asters, sunflowers, zinnias, marigolds, &c.; but on the whole it must be confessed that the majority of the plants composing the order present a weedy and unattractive appearance. Of the 26 indigenous genera 16 are widely spread; 5 extend to Australia alone (Brachycome, Olearia, Celmisia, Raoulia, Craspedia), but of these Celmisia and Raoulia are very feebly represented outside New Zealand. One genus (Cassinia) reaches South Africa as well as Australia; one (Abrotanella) occurs in Australia, Tasmania, and antarctic South America. The three remaining (Pleuropkyllum, Haastia,. Br achy glottis) are endemic. Many weeds of cultivation belonging to the order have become naturalised in the colony, a list of over 60 species being given in the appendix. Most of these are from the Northern Hemisphere, and descriptions of nearly all will be found in any British Mora.
Owing principally to the large size and homogeneous character of the order, very great difficulty has always been experienced in arranging the species in suitable genera and tribes, and the classification is still in an unsettled state. As, there are no important differences in the flower and fruit, it becomes necessary to use minor characters, such as the shape of the style-branches; the sexual, differences of the florets composing the heads; the shape of the corolla; the absence or presence of minute tails to the anthers; the various modifications of the pappus; and the minute differences in the shape and sculpture of the ripe fruit or achene. Considerable practice is required before these distinctions can be understood, and a beginner will find it no easy matter to refer the species to their proper genera. His best plan will be to induce some friend to name a few for him, and then to carefully compare these with the specific, generic, and page 269ordinal characters given in this book, or in other works on the flora. By so doing he will insensibly acquire a practical knowledge of the characters used in distinguishing the species and genera which will ultimately enable him to-identify them for himself. In using the subjoined key to the New Zealand genera it must be remembered that the minute differences in the shape of the style-branches, so largely employed to separate the tribes from one another, can only be observed in the hermaphrodite florets, the style of the female florets being very similar throughout the order.