DICOTYLEDONS: METACHLAMYDEAE 263 



(S. Jacobaea), belonging to the same genus, has conspicuous 

 flowers with ligulate ray-florets and is pollinated by insects. 



In a few cases the fruits are dispersed by animals ; 

 e. g. the Bur Marigold (Bidens tripartita) has hooked fruits 

 and in the Burdock (Arctium spp.) the bracts end in recurved 

 hooks and the whole head may be dispersed. 



Many Composites are cultivated for their flowers, e. g. 

 Sunflower, Aster, Dahlia, Chrysanthemum, and Cornflower. 



Some are interesting Alpine plants, like the Cudweeds 

 (Gnaphalium spp.) and the Edelweiss (Leontopodium 

 alpinum) . 



The young flower-heads of the true Artichoke (Cynara 

 Scolymus) are eaten. The Jerusalem Artichoke (Helianthus 

 tuberosus) has underground tuberous stems with ' eyes ' 

 like the potato (see p. 130). 



The Metachlamydeae or Sympetalae, which contains 

 more than 42,000 species, shows much greater uniformity 

 of flower-structure than does the Archichlamydeae. 

 The parts of the flower are definite in number and cyclic ; 

 the corolla is usually gamopetalous and the stamens 

 epipetalous. The ovules have a single integument. The 

 more simple forms, including the Heath and Primrose, have 

 hypogynous flowers, the parts are in five cycles or whorls, 

 two of which are stamens, and the number of the carpels is 

 the same as in the other whorls. In the orders to which 

 belong the Lilac, Forget-me-not, Deadnettle, Nightshade, 

 and Speedwell, the flowers are hypogynous, the parts are 

 in four cycles, the carpels fewer than in the other whorls. 

 In the higher types the flower is zygomorphic. The 

 highest stage of development is reached in the order Com- 

 positae, the flowers of which possess the following com- 

 bination of characters : the corolla is gamopetalous and 

 epigynous, and the anthers are syngenesious. The fruit 

 is small, seed-like, and often provided with a pappus. The 

 inflorescence consists of a large number of small dimorphic 

 flowers condensed into a compact head. 



