AGGREGATE. 573 



E. AsTEREa: have a bristle-like, unbranched pappus, often of a 

 dingy brown ; receptacle naked ; involucral leaves numerous, im- 

 bricate. Solidago (Golden-rod) ; capitula small, yellow-flowered, 

 borne in panicles. Aster; disc-flowers most frequently yellow, 

 ray-flowers violet; Callistephus ; Erigeron (Flea-bane) Inula. 

 All the corollas are tubular in : Gnaphalium (Cud-weed) ; involu- 

 cral leaves dry, rattling, often coloured; the foliage-leaves and 

 stem often white with woolly hairs ; ray-flowers ? , with narrow, 

 tubular corolla; disc-flowers $ (few). Antennaria (Cat's-foot ; 

 dioecious), Filago, Helichrysum, Ammobium, Rliodanthe and others. 

 Leontopodium (L. alpinum, " Edelweiss "'). 



F. AMBKOSIE^E, a very reduced type of Composite, differing from the others 

 in having free anthers ; the-capitula are generally unisexual, monoecious, the $ 

 borne in a terminal inflorescence, the ? in the leaf-axils. In other respects 

 they are most closely related to Helianthece. Xanlhium. In the $ -capitula 

 there are many flowers without calyx, but with tubular corolla and free invo- 

 lucral leaves. In the $ -capitula there are only 2 flowers, which are entirely 

 destitute of both calyx and corolla ; involucral leaves 2-spined, united to form 

 an ovoid, bilocular envelope, each compartment containing one flower. The 

 envelope of involucral leaves unites with the fruits, enclosing them at maturity 

 with a hard covering from which numerous hook -like spines project, assisting 

 very greatly in the distribution of the fruit. The whole structure thus finally 

 becomes a 1- or 2-serded false nut. Ambrosia, the ? capitulum 1-flowered. 



POLLINATION. The flowers are somewhat insignificant, but become very con- 

 spicuous owing to a number being crowded together in one inflorescence. The 

 corollas of the ray-flowers, being often very large (Asterece ; Centaurea), fre- 

 quently render the capitula still more conspicuous. The capitula display many 

 biological phenomena similar to those often shown by the individual flowers in 

 other orders, e.g. by periodically opening aud closing, in which the involucral 

 leaves resemble the calyx in their action. (The name " Compositae " originates 

 from the term " flos compositus," composite flower). An abundance of honey 

 is formed, which to some extent fills up the corolla-tube, and since insects may 

 visit a number of flowers in the course of a short period they are very fre- 

 quently visited, especially by butterflies and bees. The pollination has been 

 described on page 567. Protandry is universal. In the bud the tips of the 

 styles, covered by the sweeping-hairs, lie closely enveloped by the anther-tube ; 

 in the next stage the style grows through the tube and sweeps out the pollen as 

 it proceeds ; ultimately the stylar branches expand and the stigma is then pre- 

 pared to receive the pollen. In many, the sensitiveness of the filaments assists 

 in sweeping out the pollen at the exact moment of the insect visit. Regular 

 self-pollination is found e.g. in Senecio vulgaris j wind-pollination e.g. in 

 Artemisia and the plants related to it. 



This extremely natural and well-defined order is the largest (and no doubt 

 one of the youngest?) ; it embraces 10-12,000 known species (in 770 genera), or 

 about one-tenth of all Flowering-plants. They are distributed over the whole 

 globe, but are most numerous in temperate countries ; the majority prefer open 



