482 



THE RUBIALES 



alterations made that lead up to the specialized types. Look 

 back over the preceding groups and orders and note that many 

 of the irregular types of flowers are preceded by a long series 

 of regular forms. So in the madder order, this new departure 

 of the flower is attended with such a simplicity of structure as 

 to render difficult the separation of some of the genera from the 

 open flowers of the Umbellales which have also arrived at the 



B 



FIG. 335. Simpler forms of the Rubialcs: A, inflorescence of the arrow- 

 wood (Viburnum). B, simple, epigynous flower of the elderberry (Sam- 

 bucus) o, ovary. C, the twin flower (Linnaea). 



same stage of development, page 465. This would not necessarily 

 imply a relationship, since it repeatedly happens both among 

 plants and animals that identically similar structures arise in 

 groups in no way related. From these simple flowers, that may 

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

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

 tonia), buttonbush (Cephalanthns] , twin flower (Linnaea, Fig. 

 335> Oi snow r berry (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- 



