Asteridae: Scrophulariales. The Acanthaceae are mostly herbs or shrubs comprising about 250 genera and 2,500 species, including twining forms. The leaves are simple, opposite and decussate; stipules are lacking. The flowers are bisexual, zygomorphic, and usually are associated with conspicuous, often brightly colored bracts. The calyx is usually deeply 4-5 lobed or sometimes is highly reduced with more numerous minute teeth. The corolla is sympetalous, usually 5-merous, mostly zygomorphic, and commonly 2 lipped. The androecium usually consists of 4 didynamous stamens or only 2 stamens adnate to the corolla tube or epigynous zone, alternate with the lobes. The gynoecium consists of a single compound pistil of 2 carpels, a single style, and a superior ovary with 2 locules, each with usually 2-10 axile ovules in one or two collateral vertical tiers. An annular nectary disk is usually found around the base of the ovary. The fruit is commonly an elastically dehiscent loculicidal capsule. The seed stalk or funiculus of each seed is modified into a hook shaped jaculator or retinaculum that functions in flinging out the seeds during dehiscence.
Each "thumbnail" image below is linked to a larger photograph.
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Justicia betonica, white shrimp plant. Note the conspicuous bracts, the strongly two-lipped corollas, and the didynamous stamens. | ||
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Justicia brandegeana, red shrimp plant. The bracts in this species are quite showy and are at least as conspicuous as the 2-lipped corollas. | ||
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Asystasia gangetica, Chinese violet. The small bracts in this species are not typical for the family. However, the very deeply 5-lobed calyx is. The photo on the right shows the fruit after dehiscence. Notice the persistent calyx and the well developed jaculators upon which the seeds rested before the explosive separation of the carpels hurled the seed out of the capsule. | ||
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Sanchezia speciosa. This species has narrowly tubular flowers that are only weakly zygomorphic. The bracts are reddish orange like the calyx and are therefore not particularly conspicuous. | ||
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Graptophyllum pictum, caricature plant. The zygomorphic, strongly 2-lipped flowers of this species are much more conspicuous than the floral bracts. | ||
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Hemigraphis alternata, metal leaf. This common ground cover has purplish bracts that are about as conspicuous as the flowers. | ||
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Adhatoda cydoniaefolia, Brazilian bower plant. | ||
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Pseuderanthemum atropurpureum, purple false eranthemum. Smooth shrub from S. Polynesia, with rose-purple or white and purple flowers; leaves variegated with purple or green and white. | ||
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Thunbergia laurifolia, laurel-leaved thunbergia, purple allamanda. The calyx is typically extremely reduced in this genus. |
