COMPOSITAE 



165 



importance in classification of the fam. It may be smooth or hairy, 

 &c. ; there may (Helianthus, &c.) or may not (Calendula, &c.) be, 

 upon it, scaly br. belonging to the individual firs. In Cynareae these 

 br. are divided so as to form numerous bristles. 



In the simplest case the fls. of a single head are all alike and , 

 but there are many deviations from this type. The fls. may be all 

 actinomorphic (tubular') or all ] (ligtilate) ', see below. Very commonly 

 however, as in daisy or sunflower, there is a distinction into a disc of 

 actinomorphic fls., and a marginal ray of -|- fls. Or, as in Centaurea 

 sp., the outer florets may be actinomorphic but different in size from 

 the central. The number of ray-florets varies in different sp., but 

 according to definite rules. 



The distribution <>/" sexes among the fls. of a head varies much. 

 The most common case is gynomonoecism, the ray-florets ?, the 

 disc ?. The very large ray-florets of Centaurea sp. and others are 

 completely sterile (cf. Hydrangea, Viburnum, &c.). Cf. also Tussi- 

 lago, Petasites, &c. 



Tlas Jhnoer is fully epig., usu. j-merous. K absent in Ambrosia 

 and its allies, Siegesbeckia, &c. ; in some cases 

 it appears only as a slightly -globed rim upon 

 the top of the inf. ovary (cf. Rubiaceae and 

 Umbelliferae) ; usu. it takes the form of hairs 

 or bristles the pappus and enlarges after fert. 

 into a parachute (Dandelion) or into hooked 

 bristles (Bidens) to aid in clistr. (see below). 

 C (5), valvate in bud; actinom. (tubular) or [ . 

 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 with 5 teeth at the end repres. 

 the petals, but is usu. also given to those lipped 

 forms where the lower lip is strap-shaped and 

 ends in 3 teeth. Sta. 5, epipet. with short 

 filaments, alt. with the petals. Anthers intr., cohering by their 

 edges (syngenesious), forming a tube around the style (cf. Lobelia). 

 G (2), with a simple style that forks at the end into two stigmas, an 

 ant. 'and a post, (see diagram). The construction of the style and 

 stigma is of importance in the classification. There is often a brush 

 of hairs on the style below the stigmas. Only the inner (upper) 

 surfaces of the stigmas are as a rule receptive to pollen. Ovary i-loc. 

 with i erect, basal, anatr. ov., which gives an exalb. seed with 

 straight embryo, enclosed in the dry indeh. pericarp. This fr. is usu. 

 termed an achene, but of course is, if one adhere strictly to definitions, 

 a pseudo-nut, as its pericarp is partly axial, and there is > one cpl. 

 It is often crowned with a pappus (see below). 



Natural History of the Flower. Being massed together in heads, 

 the individual fls. may be, and usu. are, comparatively very small, 

 and the advantage is gained that a single insect visitor may fert. 

 many fls. in a short time without having to fly from one to the other, 

 while there is no loss of conspicuousness, and a considerable saving 



Floral Diagram of 

 Composite fl. with pap- 

 pus (after Eichler). The 

 small outer lines repre- 

 sent the pappus-bristles. 



