486 



THE CAMPANULALES 



flowers in heads subtended by one or more rows of bracts that 

 form a calyx-Hke involucre (Fig. 338, in). This type of in- 

 florescence might readily be mistaken for a single floAver as the 

 buttercup, rose, etc. This tendency to group the flowers in 

 heads and compact clusters has been attained in several orders, 

 notably the mustards, peas, Umbelliferae, mints, scrophularias, 

 and especially in the teasel family, page 482. But in no group 

 has the aggregation been so successful and coupled with such 

 efficient types of flowers. Leaving out of consideration the de- 

 generate ragweeds the individual flowers of a head are very 



Fig. 339. Flowers and fruit of Taraxacum: A, sectional view of inflor- 

 escence — in, involucre. The flowers in the center of the head not as yet in 

 bloom. B, an unopened flower. The thread-like calyx (pappus) and corolla 

 arising from the ovary, 0. C, corolla opening. D, later stage, the style has 

 elongated, sweeping the spores from the sheath of anthers, an, and the two 

 stigmatic lobes are beginning to open. E, flower in full bloom, the stigma 

 lobes recurving. 7^, mature fruit. The pappus is lifted up on a long, slender 

 outgrowth of the ovary, 0. 



uniform in structure. They are epigynous, parts usually in fives, 

 calyx wanting or more often appearing as tufts of hairs, plumose 

 or barbed bristles, and known as the pappus (Figs. 339, 341). 

 The corolla is tubular or partially split open, forming a strap- 



