DEVELOPMENT OF PLANTS 487 



shaped blade known as the ligulate corolla (Fig. 339, £). The 

 anthers are united about the style which is often hairy and pushes 

 out the microspores like a piston (Fig. 341, B-D). The style 

 is two-lobed, the stigma usually appearing as a line on the inner 

 surface of the lobes and the single, one-ovuled carpel matures 

 as an akene. Scale-like bracts, the chaff, are often associated 

 with the flowers (Fig. 341, B). The nectar formed from the 

 glands at the base of the style is concealed at the bottom of the 

 corolla tube. 



{a) The Chicory Family. — This family is distinguished by all 

 the flowers of the head being ligulate (Fig. 339) and mostly yel- 

 low in color and by the possession of milky, bitter or acrid juices. 

 Hei'e belong the goat's beard (Adopogon), hawkbit (Leontodon) , 

 sow thistle (Sonchus), hawkweed (Hieracium), rattlesnake root 

 ( Nabalus) , as well as several introduced and native plants that 

 are cultivated, as the dandelion (Taraxacum), species of chicory 

 (Cichorium), salsify (Tragopogon), lettuce (Lactiica). The char- 

 acter of the head, flower and fruit of this family are well shown 

 in the dandelion (Fig. 339). All the flowers are ligulate, the 

 five lobes frequently to be seen on the margin of the corolla 

 indicating the number of petals, and the calyx assumes the forni 

 of minute hairs (Fig. 339, B-E). The five filaments adhere to 

 the tube of the coroUa while the anthers form a cylinder about 

 the style and discharge their spores before the flower opens. The 

 style begins to elongate as soon as the flower opens and pushes 

 out the spores which rtiay be seen as little piles of dust at the" 

 top of the anthers in freshly opened flowers. The filaments of 

 this genus are sensitive to touch and curve outward, pulling down 

 the sheath of anthers, thus assisting in sweeping out the spores 

 and exposing the style when an insect irritates them in his quest 

 for nectar. This device appears in other genera and is sometimes' 

 the only means of exposing the microspores and styles. Autog- 

 amy is at first impossible owing to the fact that the two lobes of 

 the style are closely pressed together effectually excluding the 

 microspores from its inner, stigmatic, surface. Later the style 

 grows considerably above the anthers and the lobes separate, ex- 

 posing the stigmas for crossing (Fig. 339, E). The association 



