DIV. II 



ANGIOSPERMAE 



713 



usually differ from one another in sex as well as in colour ; the disc-florets are 

 hermaphrodite, the ray-florets purely female. The flower-heads are thus hetero- 

 gamous (Matricaria, Arnica}. Lastly, the marginal 

 florets maybe completely sterile (Centaurea cyanus) 

 and serve only to render the capitulum conspicuous 

 to insects. 



One series of genera has only tubular florets in 

 the head. Carduus (Plumeless Thistle), pappus of 

 simple, hair-like bristles (Fig. 783). Cirsium, with 

 feathery pappus. Echinops, with single-flowered 

 capitula associated in numbers. Lappa (Burdock), 



FIG. 782. Arnica montana. a, Receptacle of capi- 

 tulum after removal of fruit ; b, fruit in longi- 

 tudinal section, the pappus only partly shown. 

 (After BERG and SCHMIDT, magnified.) 



Fio. 783. Androecium of 

 Carduus crispus (x 10). 

 (After BAILLON.) 



involucral bracts with recurved, hook-like tips (Fig. 781 a). Cynara Scolymus 

 (Artichoke). Cnicus benedictus (Fig. 786), capitula solitary, terminal, surrounded 

 by foliage leaves. Involucral bracts with a large, sometimes pinnate, terminal 



FIG. 784. Fruits of A, Hdianthus annuus; B, Hieracium virosum; C, Cichorium Intybus. 

 (After BAILLON.) 



spine and a felt of hairs. Centaurea with dry, scaly, involucral bracts and large, 

 sterile, marginal florets. 



Other genera have only hermaphrodite ligulate florets in the capitulum, 

 and have latex in all parts of the plant. Taraxacum officinale (Dandelion) is 

 a common plant throughout the northern hemisphere. It has a long tap-root, 



