Hypericum

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Hypericum

Description

Small trees, shrubs or perennial or annual herbs, glabrous (in Mal.). Bark not exuding resinous sap. Branchlets terete or 2-4-lined or -angled. Leaves opposite (rarely whorled), entire (rarely gland-fringed in extra-Mal. spp.), sessile or shortly petioled, with translucent ('pale') glands containing essential oils and sometimes black or red glands containing hypericin or pseudohypericin. Inflorescences terminal, cymose, dichasial or monochasial. Flowers (sometimes except the gynoecium) 5(-4)-merous, homostylous (in Mal.). Sepals quincuncial or rarely decussate, coriaceous to chartaceous, persistent (in Mal), glandular like the leaves. Petals yellow, often tinged red, glandular like the leaves, without nectariferous appendage (in Mal), glabrous, caducous or persistent. Stamen fascicles epipetalous, free or variously united (2 + 1 + 1 + 1 or 2 + 2 + 1 or (5) or (4)) and then with double ones episepalous, glabrous, caducous or persistent, each with 1-c. 60 stamens; filaments yellow, slender, usually united only towards the base or apparently free; anthers yellow or reddish, shortly oblong, dorsifixed or apparently basifixed (sect. Takasagoya), with amber or black gland terminating the connective. Staminodial fascicles absent (or very rarely 3, alternating with 2+2 + 1 stamen fascicles in extra-Mal. spp.). Ovary 5-3-celled or 1-celled with 5-3(-2) parietal placentas; styles 5-3(-2), free or ± united, ± slender; stigma small, flat or ± capitate. Ovules oo-2 on each placenta, horizontal. Fruit a septicidal 5-3(-2)-valved ± coriaceous capsule (rarely tardily dehiscent or ± baccate in extra-Mal. spp.), with ± prominent vittae in the valves. Seeds ∞-l on each placenta, curved-cylindric to ellipsoid, sometimes carinate with a membranous wing; testa variously sculptured; embryo cylindric, straight or curved, with cotyledons usually shorter than the hypocotyl.

Distribution

Asia-Tropical: Australasia: present e.g. the Amazon basin: absent throughout most of the tropical and temperate zones: present
About 400 spp. throughout most of the tropical and temperate zones, but absent from some lowland tropical areas (e.g. the Amazon basin) and rare in Australasia (2 native species, here spp. 14 and 15), in Malesia 13 spp. .

Notes

Hypericum, as recognised here, is identical with ENGLER'S Hypericeae except for Hypericum sect. Elodea (JUSS.) CHOISY, which, as the genus Triadenum RAFIN., belongs in the Cratoxyleae and appears to be a herbaceous derivative of Cratoxylum.
The geographical relationships of the Malesian species are interesting. Sect. Ascyreia (Sumatra to SW. Celebes) also occurs in south continental Asia, Taiwan, Ceylon, Turkey, and Socotra. Sect. Takasagoya (Philippines) is otherwise confined to Taiwan. Sect. Hypericum (Philippines, Sabah, Sumatra) is pan-boreal in distribution; but the Philippine species is found elsewhere only in Taiwan and Japan, whereas the species of Sabah and Sumatra is otherwise eastern Himalayan in distribution. One of the two species of sect. Brathys, which also occurs from Japan to Ceylon and in Australia, New Zealand and Hawaii, is closely related to a species of southeastern U.S.A., whereas the other has a mainly southern distribution (Australia, New Zealand, New Caledonia, New Guinea) with outliers in South and East Asia (eastern Himalayas, Vietnam, Taiwan) and affinities with western South America. The affinities of the remaining section, sect. Humifusoideum, lie in quite a different direction, namely with Africa. The New Guinea species form a closely related group which appears to be derived from sect. Campylosporus of Africa, Madagascar and the Mascarene Islands. In addition, however, there are three species of sect. Humi-fusoideum in Africa and Madagascar (H. natalense WOOD & EVANS, H. wilmsii R. KELLER and H. peplidifolium A. RICH.), which are apparently derivatives, in turn, of this New Guinea group. The relationships therefore are Africa→ New Guinea -> Africa. This New Guinea group also appears to have given rise to two other species, H. pulogense MERR. (Philippines) and H. beccarii N. ROBSON (Java, Sumatra).
Hybrids of Hypericum species have been found from time to time in nature, but only between rather closely related species. Artificial hybrids are not always easy to produce, but some 'wide' crosses have been successful. The resultant plants, however, are usually weak and have always proved sterile. Some artificial crosses between closely related species, however, have thrived, and one or two are well-known garden plants. In general, apart from the hybrids involving H. perforatum L., which is largely pseudo-gamous and produces n and 2n gametes, crosses are likely to be successful only between species with the same chromosome number.

Citation

L.f. - in Ann. Sc. Nat. 1836: 366
Y. KIMURA - in Nakai & Honda, Nova Fl. Jap. 10. 1951: 108
Y. KIMURA - in Nakai & Honda, Nova Fl. Jap. 10. 1951: 229
MIQ. - in Fl. Ind. Bat. 1859: 513
Y. KIMURA - in Nakai & Honda, Nova Fl. Jap. 10. 1951: 85
L., Sp. Pl. 1753: 787
R. KELLER - in E. & P., Nat. Pfl. Fam., ed. 2, 21. 1925: 175
SPACH - in Ann. Sc. Nat. 1836: 363
SPACH - in Hist. Nat. Vég. Phan. 1836: 446
Y. KIMURA - in Nakai & Honda, Nova Fl. Jap. 10. 1951: 96
ENGL - in E. & P., Nat. Pfl. Fam., ed. 2, 21. 1925: 174
ROBSON - in Blumea. 1972
L., Sp. Pl. 1753: 272
LINNE, Sp. Pl. 1753: 783