|MadSci Network: Botany|
Both the cactus family and euphorbia or spurge family are large diverse families. Some main differences are that cacti usually have clear, watery sap and many euphorbs have milky, sticky sap that is often toxic. Cactus spines occur in clusters of more than two on an aerole, an extremely short shoot. Euphorb spines are modified stipules and occur in pairs, and have no aeroles. Flower structure also varies between the two families. The characteristic euphorb inflorescence is termed a cyathium, which appears as one flower but is several. Flowers lack petals. The female flower is elevated on a stalk and surrounded by tiny male flowers each consisting of just an anther. The flowers are then surrounded by cup-like leaves. In contrast to small flowers and inflorescence of euphorbs, cactus flowers are usually large single flowers with petals and many stamens. Cacti are native almost exlusively to dry areas of America while Euphorbia are native throughout the world in both wet and dry areas. Cactus-like euphorbs are found in Africa. The majority of cacti are succulents with fleshy stems adapted for water storage and photosynthesis and leaves reduced to spines or needles. Some euphorbs are succulents but many have broad leaves and are not succulent, such as poinsettia (Euphorbia pulcherrima), castor bean (Ricinis communis), snow-on-the-mountain (Euphorbia marginata), rubber tree (Hevea brasiliensis) and the houseplants croton (Codiaeum variegatum) and chenille plant (Acalypha hispida). References Cacti ARE Succulents Euphorbia Poinsettia Euphorb Houseplants Euphorbiaceae - the Spurge Family Euphorbiaceae Cactaceae
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