596 



BOTANY 



South American family, which is only of interest as establishing the connection 

 between the Dipsacaceae and Compositae. 



Family Compositae. '- — Flowers without epicalyx ; corolla 



VALVATE ; stamens FIVE, WITH SYNGENESIOUS ANTHERS ; Style BIFID ; 



ovules erect ; seeds without endosperm. Leaves commonly 

 alternate (Figs. 589-594). 



The Compositae comprise mostly herbs, rarely, and then usually con- 

 fined to the Tropics, shrubs, lianes, and trees. The vegetative organs 

 vary so greatly in their external appearance that they furnish no features 

 that are valuable as a means of distinguishing the family ; chemically, 

 however, the Compositae are characterised by the presence of inulin in 

 their subterranean parts. The flowers and inflorescences, on the other 



C 



Fig. 591. — Arnica montana. o, Ray-flower; b 

 di.sc-flower ; c, the same cut through longi 

 tudinally. (After Berg and Schmidt, mag 

 nifted.) 



Fig. 592. — Arnica 'Montana, a, Receptacle of 

 capitulum after removal of fruit ; b, fruit in 

 longitudinal section, the pappus only partly 

 shown. (After Berg and Schmidt, magni- 

 fied.) 



hand, although they also exhibit great diversity of form, are always 

 easily recognisable. The heads (Fig. 590) are either solitary or com- 

 bined in compound inflorescences, generally of a dichasial character. 

 The involucral bracts are sometimes herbaceous and green ; sometimes 

 scarious and then often highly coloured, as in Helichrysum and other 

 genera ; sometimes, as in many species of Centaurea, they are provided 

 with dry fringed margins, or, as in the Thistle, they may be prickly. 

 The expanded floral axis, the receptacle of the capitulum, is concave or 

 flat (Fig, 590, a), slightly elevated or prolonged conically. It is some- 

 times naked (a) or hairy, sometimes covered with small scales (&), 

 always pitted like the surface of a thimble, with alveoli in which the 

 separate flowers are inserted. The calyx is never green, and is only 

 rarely represented by five colourless segments. It usually consists of 

 a cushion-like ring which bears the pappus, a tuft of bristles or hairs 

 (Fig. 591). The COROLLA is often regular and five-lobed (Fig. 591, b), 

 as in the Thistle. When zygomorphic, it may be bilabiate, as in the 

 South American Mutmeac ; more frequently, by the suppression of the 



