Changes

:Chromosome number: ''x''= 11;''I. chinensis'', ''I. coccinea'', ''I. javanica'', ''I. nigricans'': 2''n''= 22

*''Ixora chinensis'' Lamk, *''I. coccinea'' L., *''I. javanica'' (Blume) DC., *''I. longifolia'' J.E. Smith, *''I. nigricans'' R.Br. ex Wight & Arn.

''Ixora'' species are well known as ornamentals (e.g. ''I. chinensis'' , ''I. coccinea'' , ''I. javanica'' ), and are commonly planted in gardens, parks and along roadsides. The fruits of ''I. philippinensis'' Merr. are edible. The wood of ''Ixora'' is occasionally used, often for implements and comparatively small objects; only a few species reach timber size.

In a modified tumour promotion test, complete inhibition of all kinds of tumours was exhibited by decoctions of flowers of ''I. coccinea'' and ''I. chinensis'' . The antitumour factor from ''I. javanica'' flowers showed broad activity against transplantable solid tumours in mice by inhibiting the growth of tumours and arresting the growth of already formed tumours; it showed lesser activity against ascites tumours. In vitro studies showed 50% cytotoxicity to Dalton's lymphoma and Ehrlich ascites tumour cells at concentrations of 12 μg and 65 μg, respectively, with no activity against normal lymphocytes but preferential activity against lymphocytes derived from leukaemia patients and K 562 suspension cell culture. Topical application of 100 mg/kg body weight of ''I. javanica'' flower extract inhibited the growth and delayed the onset of papilloma formation in mice initiated with 7,12-dimethylbenz-α-anthracene (DMBA) and promoted by using croton oil. When administered orally at the same dose the extract significantly inhibited the growth of soft tissue fibrosarcomas induced by subcutaneously injected 20-methylcholanthrene. Oral administration of 200 mg/kg of the extract inhibited the growth of intraperitoneally transplanted sarcoma-180 and Ehrlich ascites carcinoma tumours and also showed an increase in the life span of the treated mice. Toxicity studies showed that the blood urea nitrogen levels were elevated after treatment. Furthermore, tritiated thymidine incorporation studies indicated that the mechanism of action of the factor is at the site of DNA synthesis. The purified fractions contained ferulic acid, pyrocatechuic acid and caffeic acid. The compounds responsible for the inhibitory effects on tumour growth were identified as ferulic acid (4-hydroxy-3-methoxycinnamic acid) and its structural isomer, 3-hydroxy-4-methoxycinnamic acid.

*Shrubs to small or sometimes medium-sized trees up to 25 m tall; bark surface smooth, lenticellate, fissured or scaly, greyish-brown; twigs terete, often with series of rather close, leafless nodes especially at branching points. *Leaves opposite or sometimes in whorls of 3, simple, entire, broadly elliptical to linear, herbaceous to coriaceous, base usually acute or cuneate, apex obtuse to acute, acuminate or caudate, almost always glabrous; petiole usually present, concave or canaliculate; stipules interpetiolate, connate at base, distinctly cuspidate or with a long, stiff, needle-like extension at the tips. *Inflorescence a terminal corymb or corymbose panicle, peduncle short with an erect inflorescence or longer with a nodding or pendulous inflorescence, often puberulous or pubescent, usually 45-300-flowered. *Flowers often 3 together, bisexual, 4-merous, fragrant or not, protandrous; calyx often divided to the base; corolla with a cylindrical tube, lobes contorted in bud, spreading and flat or reflexed in the open flower, often white but sometimes pink, yellow or red; stamens inserted at corolla throat, with short filaments, anthers dorsifixed, sagittate and reflexed, usually yellow; disk annular; ovary inferior, 2(-3)-locular with 1 ovule per cell, style filiform, slightly exserted from the corolla tube, the exserted part not longer than the corolla lobes, stigma 2-lobed, the lobes linear and recurved. *Fruit a globose to 2-lobed drupe, 5-15 mm in diameter, ripening red to black, with 1-2 pyrenes; pyrenes 1-seeded, thin-walled, plano-convex, with a round excavation inside. *Seed with thin testa, endosperm entire. *Seedling with epigeal germination; cotyledons leafy, green.

''Pavetta'' closely resembles ''Ixora'' , but can be distinguished by its long-exserted style with coherent stigmas, whereas the anthers are conspicuously twisted. The differences between the widely cultivated ''I. chinensis'' and ''I. coccinea'' are sometimes obscure as a result of selection for rare or extreme forms. Accidental or deliberate hybridization appears to occur.

''Ixora'' species are usually confined to lowland and lower montane forest up to 1700 m altitude. Some species are also found in swampy locations in the vicinity of rivers or occasionally in rice fields (e.g. ''I. grandifolia'' ).

*M.C. Ysrael & J.L.C.H. van Valkenburg