Published online by Cambridge University Press: 06 July 2012
The highly specialised features of the Compositæ leave little room for doubt that the family is an advanced one, and it is not without significance that the vast majority of its species should be herbaceous plants; shrubby species are infrequent, while trees are of the rarest occurrence. The markedly herbaceous habit is further emphasised if attention is confined to the large and widespread genus Senecio, comprising over 2000 species, for, although they include plants of very diverse habit, few attain to tree dimensions, or possess a well-developed, perennial, woody trunk. Herbs or shrubs account for 99 per cent, of the species, the former greatly predominating. The remainder comprises a small group of about 20 species, which have assumed the arborescent habit.