450 



THE RUBIALES 



be no more sympetalous than certain genera of the carrot order, 

 we pass to more pronounced tubular forms in the bluets (Hous- 

 tonia), buttonbush (Cephdlanthus), twin flower (Linnaea, Fig. 

 335. O snowherry (Symphoricarpus) and finally to irregular 

 and even labiate types as in the honeysuckle (Lonicera, Fig. 

 '268), valerian, teasel (Dipsacus) and scabious (Fig. 336). It 

 is noteworthy that in the three latter genera the flowers become 

 massed in a dense inflorescence, known as a head, which are sub- 

 tended by modified leaves, the involucre (Fig. 336) and the pistils 

 are reduced to a single fertile carpel with two-lobed style. These 



FIG. 336. Advanced forms of the Rubiales : A, inflorescence of Scabiosa, 

 at the right showing the involucre, in. B, a single flower enlarged, show- 

 ing the somewhat irregular corolla. At the right the sectional view of 

 the flower shows the calyx, ca, terminating in bristle-like teeth; br, bract- 

 like cup surrounding the calyx. C, irregular flower of valerian n, nectar 

 sac; ca, rudimentary calyx, which matures in the fruit as a mass of deli- 

 cate feathery organs, known as the pappus. 



variations will become very prominent in the next order. The 

 Rubiales are an important tropical group and furnish the coffee 

 (Coffea) and the cinchonas which yield such drugs as quinine 

 and calisava. 



