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A TEXTBOOK OF THEORETICAL BOTANY 



More common and important than the above are the cases of sepaline 

 plumes, so characteristic of the Compositae and found in divers other 

 famiHes. The cypsela of Composites is an inferior fruit and thus the calyx 

 stands on top of it. In some genera there is only the merest trace of sepals, 

 or none, but in a vast number of genera the calyx takes the form of a silky 

 mass of hairs, the pappus, which provides a parachute for each fruit. 

 Other families in which the fruit may have a pappus, often indistinguish- 

 able from that in Compositae, are Valerianaceae, Amarantaceae and Pro- 

 teaceae. 



Among Compositae the pappus takes all sorts of forms, from a few 

 simple hairs or a ring of wing-like scales in Ursinia, to a most complex 

 structure in Taraxacum and Tragopogon (Fig. 1418), in which the base of 



Fig. 141 8. — Tras^opogon prateiisis. Fruiting capitulum. I'^ach 

 fruit bears a parachute-like pappus. 



the calyx elongates into a fine tube, the top of which is set with thickly- 

 branched radiating ribs, like an umbrella. The pappus of Tragopogon is one 

 of the most complex and the ribs are even adjustable by hygroscopic pulvini 

 (Fig. 141 9). The pappus is an extremely effective means of dispersal, 

 especially if the fruits are light, and by its aid they can be carried by the 



