Melastoma tetramerum Hayata
Table of contents
1. Protologue
Melastoma tetramerum Hayata, Ic. Pl. Formos. 3 (1913): 120. - Type: Hattori s.n., Chichijima-Hatsunejima, Bonin Islands, Japan, Juli 1905 (TI, not seen)
Rami et ramuli tereto-tetragoni pilis adpressis strigosis obtecti, cortice fusco-rubescenti demum gradatim soluto. Folia opposita ovato-elliptica vel oblonga 4 cm longa 1,5 cm lata chartacea apice acuta basi obtusa margine integra supra adpresse regulariter pilosa subtus dense adpresse pilosa distincte 3-nervia, praetera 2-marginalibus tenuibus instructa, nervis omnibus subparallelibus deorsum ± divergentibus sursum convergentibus ad apicem foliorum attingentibus supra subimpressis subtus elevatis dense adpresse pilosis, petiolis 7 mm longis supra sulcatis subteretibus. Flores ad apicem ramulorum axillarium solitarii vel terminales, pedunculis 1-2 cm longis. Calyx-tubus globoso-urceolatus 7 mm longus latior quam extus adpresse pilosus basi rotundatus, ore plus minus contracto, limbo 4-lobato, lobis triangulari-lanceolatis 12 mm longis basi latissimis 5 mm latis extus adpresse strigoso-pilosis intus glabris, sed sursum adpresse pilosis. Petala 4 obovato-rotundata 22 mm longa 18 mm lata apice rotundata basi contracto-unguiculata, (unguibus 2 mm longis), margine sub lente minute cilolata. Stamina 8, iis cum petalis alternis longioribus, iis cum petalis oppositis brevioribus; stamina longiora: filamentis 7 mm longis complanatis 1 mm latis cum connectivis angulo recto articulatis, connectivis basi antherae longe productis (partibus productis 9 mm longis 1 mm latis complanatis prope basin cum filamentis articulatis) basi facie 2-cornuto-calcaratis, calcaribus obtusis 2-cornutis 1 mm longis, antheris linearibus complanatis 7-8 mm longis basi 1,5 mm latis apice obtusis basi 2-lobatis facie undulatis dorso planis apice 1-porosis; stamina breviora: filamentis 6,5 mm longis complanatis cum connectivo angulo recto articulatis, connectivis ultra basin antherae productis, partibus productis 1 mm longis recurvis basi facie 2-cornuto-calcaratis, antheris ovato-linearibus 6 mm longis basi 1,5 mm latis apice obtusis basi 2-lobatis facie transverse undulato-rugosis. Ovarium ovato-globosum 5 mm longum cum calycis tubo adnatum sursum liberum strigoso-tomentosum apice ad centrum stylum elongatum emittens, 4-loculare, loculis (infinity)-ovulatis, stylo columnari-filiformi 18 mm longo apice truncato obtuso.
Hab. Bonin: Chichijima-Hatsunejima, Juli 1905, leg. H. Hattori.
Very distinct for its tetramerous flowers and its leaves which are much smaller than those of any species of the genus.
2. Synonyms
- Melastoma tetramerum var. pentapetalum Toyoda, J. Jap. Bot. 58 (1983): 95. - Melastoma pentapetalum (Toyoda) T. Yamaz. & Toyoda, J. Jap. Bot. 62 (1987): 118. - Type: Toyoda s.n., Chibusayama, Hahazima, Ogasawara, Bonin Islands, Japan, 400 m, 15 Jul 1969 (TI, not seen)
3. Vernacular names
No vernacular names known!
4. Description
Shrub; young branches quadrangular, covered with appressed to spreading brown bristles, bark brown; old branches terete; internodes short (< 5 MM). Leaves elliptic, small, 1.9--2.6 x 0.7--0.9 cm, base rounded, apex acute; lamina strigose on both sides; nerves 5, covered with short appressed bristles; petiole 4--7 mm long. Inflorescence a terminal cyme of 2--3 flowers or flowers solitary. Flowers 5-merous; bracts not seen. Hypanthium campanulate, 8--9 x 7--8 mm, covered with spreading, thick-based bristles or penicillate emergences intermixed with much smaller spreading bristles; sepals deciduous, triangular, c. 7 x 3 mm, on the outside covered with 1--2 mm long bristles, inside glabrous; intersepalar emergences penicillate, c. 2 mm long. Petals obovate to cuneate, 18--20 x 15--19 mm, ciliate at the apex, purple. Stamens dimorphic; longer outer stamens with c. 8 mm long anthers, connective c. 10 mm long, ventrally curved, with a ventral bilobed appendage c. 3 mm long, filaments 7--8 mm long; shorter stamens with c. 4 mm long, straight anthers, c. 6 mm long, connective c. 0.5 mm long, with two ventral appendages c. 1 mm long, filaments c. 6--7 mm long. Ovary shorter than the hypanthium, crowned by golden bristles. Style c. 16 mm long. Fruits not seen, presumably fleshy capsules.
5. Distribution, ecology and notes
Distribution - Japan: Bonin Islands.
Click to see a larger map. Map made with Online Map Creation.
Ecology - Collections: 2. At altitudes from 100--450 m.
Notes - The combination of small hypanthium bristles with much larger, sometimes penicillate emergences was only found in the two cited collections of M. tetramerum from the Bonin Islands and consistently distinguish this species from its congeners.
6. Collections
JAPAN
- Coll. ign. 184105, Bonin Islands (MO)
- Murata 592, Isl. Haha-jima, en route from Oki-mura to Mt. Chibusa-yama, Bonin Islands, 462 m (L, MO)
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