Compositae, or Asteraceae - aster family

Compositae, or Asteraceae - aster family

Belong to asterids (Asteridae). More than 20,000 species—second place in flow-ering plants. Cosmopolitan, but better represented in temperate and subtropical regions. Prefer open spaces. Herbs, rarely woody plants; store carbohydrates as inulin (not starch), sometimes have resin or laticifers (subfamily Cichorioideae). Leaves are alternate or opposite, without stipules, with pterodromous venation.

Flowers in involucrate heads which mimic one flower (Fig. 8.20). Calyx reduced to hairs or bristles (pappus), petals fused in tube or ligula (with 5 or 3 teeth). Stamens 5, fused by anthers. Pistil has 2 carpels, ovary inferior. Fruit is ach-ene, mature seed has almost no endosperm. Flower formula of the tubular (disk) flower is

Ligulate (ray) flower typically has formula like

Fruit of aster family is one-seeded achene (it is a frequent mistake to call it “seed”). In achene, walls of inferior ovary are tightly fused with seed coat. Ach-enes frequently bear diverse dispersal structures: trichomes, teeth, hooks etcetera.

Oil plants, vegetables, ornamentals and medicinal plants distributed in multiple subfamilies, most important are three:

•                  Carduoideae: mostly tubular flowers

– Centaurea—knapweed

– Cynara—artichoke

– Carthamus–safflower

•                  Cichorioideae: mostly 5-toothed ligulate flowers + lacticifers with latex

– Taraxacum—dandelion

– Lactuca—lettuce

•                  Asteroideae: tubular + 3-toothed ligulate flowers

– Helianthus—sunflower (BTW, “canola”, or Brassica napus from Cru-ciferae is the second main source of vegetable oil)

– Artemisia—sagebrush

– Tagetes—marigold and lots of other ornamentals