CHAPTER XL 

 COMPOSITE (Thistle FamUy) 



The composite or thistle family is one of the largest of the 

 plant kingdom, consisting of about 10,000 species in about 

 760 genera; it has a wide geographical distribution. 



Representatives of the family are considered to be among 

 the most complex of plants, and among Dicots, of the highest 

 evolutionary rank. They show a combination of characters 

 which place them high in the scale of evolution. These are: 

 union of petals (sympetaly), inferior ovary (epigyny), seed- 

 Hke fruit, pappus, united (syngenesious) anthers, head 

 inflorescence, diclinism, and dimorphism. 



Comparatively few species of this large family are of 

 economic value. The most important are common lettuce, 

 Jerusalem artichoke, endive, salsify, and dandelion. The 

 following is a short list of the less important representatives 

 of the family: yarrow {Achillea), Chrysanthemum, sage and 

 wormwood {Artemisia spp.), sunflower {Helianthus) , Arnica, 

 Aster, goldenrod {Solidago), sow-thistle {Sonchus), Dahlia, 

 marigold {Calendula), rabbit-brush {Chrysothamnus), flea- 

 bane {Erigeron), everlasting (Antennaria), Spanish needles 

 {Bidens), and thistle {Carduus). 



Habit.— This large family is made up mostly of herbaceous 

 forms; there are a number of shrubs, however, and a few 

 tropical tree species. Many of them, as the dandelion and 

 lettuce, have a milky juice, while in others the sap is watery, 

 resinous, acrid or bitter. 



Leaves. — The leaves are either alternate or opposite, 

 rarely in whorls (verticillate) , and usually without stipules. 

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