DEVELOPMENT OF PLANTS 



475 



hooks. The Carduaceae includes a great array of plants, many 

 of which are among our troublesome weeds: Ironweed {Ver- 

 nonia), thorough wort {Eupatorium) , blazing star (Lacinaria), 

 golden-rod (Solidago), aster, fleabane (Erigeron), cat's-paw 



Fig. 341. Flowers and fruit of Bidens: A, sectional view of the inflor- 

 escence — r, ray flowers; d, disc flowers; in, bracts of the involucre. B, disc 

 flower before opening, the shaded region showing the position of the anthers 

 in the corolla — c, calyx in the form of downwardly barbed bristles; b, bract 

 or chaff associated with the disc flowers. C, early stage in the opening of 

 the flower. The stamens have been lifted beyond the mouth of the opened 

 corolla by the growth of their filaments and the style is elongating, pushing 

 out the spores, which appear in little piles at the top of the anthers. D, last 

 stage in the bloom of flowers. The style has grown beyond the anthers and 

 the stigmatic lobes have reflexed, touching the spore-covered style. E, a 

 sterile ray flower, much less enlarged. F, the fruit, showing the barbed pappus 

 for dissemination. 



