870 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



phyllaries (bracts), hermaphrodite, or pistillate, or hermaphrodite 

 with a more or less abortive pistil and functionally staminate, or neu- 

 tral (with an ovary but lacking a style and a stigma) ; corolla gamopeta- 

 lous, either regular, tubular, and 5-toothed (rarely 2- to 4-toothed), or 

 bilabiate, or Ugulate (flattened, strap-shaped, and usually 2- to 5- 

 toothed), the corolla rarely wanting in the pistillate flowers; stamens 

 (in the hermaphrodite or staminate flowers) almost always 5, united 

 by the anthers or rarely only by the filaments, inserted on the corolla; 

 ovary inferior, 1 -celled, with an erect anatropous ovule ; style normally 

 2-branched, the branches stigmatiferous inside, often bearing sterile 

 appendages at apex, the style in functionally staminate flowers often 

 undivided; fruit an achene, with a single erect exalbuminous seed, 

 usually bearing a pappus of bristles, of awns, or of scales (paleae or 

 squamellae). 



The family comprises several well-known vegetables, notably lettuce 

 (Lactuca sativa)^ artichoke (Cynara^ scolymus), salsify (Tragopogon 

 porrijolius), endive (Cichorium endivia), and Jerusalem-artichoke 

 (Helianthus tuberosus). Species of goldenrod (Solidago), rabbitbrush 

 (Chrysothamnus) , and "Colorado rubber plant" (Actinea) contain 

 appreciable quantities of rubber, but commercial exploitation of these 

 plants has not yet been found practicable. Guayule (Parthenium 

 argentatum) has been exploited extensively in the wild state in Mexico 

 and grown to a limited extent in the United States as a source of rubber. 

 The family is rich in oils, resins, and bitter principles, and many 

 species are used in medicine. The well-known insecticide, pyrethrum, 

 is furnished by the powdered flowers of a few species of Chrysanthemum. 

 Many of the family are browsed by grazing animals, but their palata- 

 bility is generally low, because of their resinous or acrid properties. 

 A few species are known to be poisonous to livestock. The ragweeds 

 (Ambrosia spp.) are notable, because their wind-borne pollen is one 

 of the most frequent causes of hay fever. Goldenrod, although popu- 

 larly regarded as an important source of hay fever, is now considered 

 to be of little if any importance in this respect. 



The flower heads are frequently showy, often beautiful, and many 

 Compositae are in cultivation as ornamentals, notably in the genera: 

 Ageratum, Anthemis, Arctotis, Aster, Bellis, Boltonia, Calendula, 

 Callistephus (China-aster), Centaur ea, Chrysanthemum, Coreopsis, 

 Cosmos, Dahlia, Dimorphotheca, Echinops (globethistle), Erigeron, 

 Felicia, Gaillardia, Gazania, Gerbera, Helenium, Helianthus (sunflower), 

 Helichrysum (everlasting, strawflower) , Heliopsis, Inula, Jurinea, 

 Krigia, Liatris (blazing-star), Ligularia, Matricaria, Notonia, Olearia, 

 Onopordon, Piqueria, Rudbeckia, Santolina, Sanvitalia, Senecio, 

 Solidago, Stokesia, Tagetes, Tanacetum, Tithonia, Ursinia, Vernonia, 

 Waitzia, Xanthisma, Xeranthemum, Zinnia. 



Key to the principal divisions 



1. Corollas of some or all of the flowers distinctly bilabiate A. 



i. Corollas not or obscurely bilabiate (2). 

 2. Flowers all hermaphrodite (perfect) and with strap-shaped 5-toothed 

 corollas B. 



2. Flowers, when hermaphrodite, with the corolla tubular and regular or nearly 

 so; marginal flowers of the head often pistillate or neutral and often with 

 strap-shaped, 2- or 3-toothed corollas (3). 

 3. Rays (strap-shaped corollas) none or the ligule vestigial (4) . 



