• inflorescence or few to many flowers borne in a head (=capitulum)
• individual flowers are often called "florets" and are of 2 types:

• 1)  disc flowers

• regular and epigynous
• no sepals as we know them, but a calyx of fluffy bristles called a pappus
• tubular corolla of 5 lobes
• stamens 5, epipetalous with the anthers connate
• pistil with  inferior ovary of 2 carpels, but ovules reduced to 1, 1 locule, stigma branched and curved
• floral formula:  -achene
• 2)  ray flowers
• identical to disc flowers except the tubular corolla is expanded on one side into a long petal lobe making the flower irregular
• floral formula:  -achene (but frequently sterile in radiate heads)

• heads of three types:
• 1) discoid heads: only disc flowers (e.g. Antennaria)
• 2) ligulate heads: only ray flowers (e.g. Taraxacum, Cichorium, Lactuca)
• 3) radiate heads: both ray and disc flowers (e.g. Senecio, Helianthus)

• mostly herbs, a few shrubs (and a few tropical trees)
• leaves simple or comound; margins entire, toothed, lobed, etc.; alternate but in some opposite or even whorled 

• the largest dicot family with 950 genera and 20,000 species
• distributed all over the earth and in almost all habitats
• food plants include lettuce, globe artichoke, endive, salsify, and chicory
• pollen of ragweed (Ambrosia)causes allergic reaction in some humans
• many weeds
• many used as ornamentals: strawflower, shasta daisy, english daisy, marigolds, zinnia

• Sunflower (Helianthus)
• Goldenrod (Solidago)
• Lettuce (Lactuca)
• Aster  (Aster)
• Ragweed (Ambrosia)
• Marigold (Tagetes)
• Blue Mink (Ageratum) 

Links