Biophytum
Description
Erect annual herbs or usually sympodially branched dwarf shrubs.
Leaves paripinnate in tufts at the end of the stem or branches, with setaceous stipules;
Flowers terminal in a usually peduncled, bracteate pseudo-umbel, heterodi-, tri- or homostylous.
Sepals glabrous inside, ± free.
Petals contort, glabrous, coherent above the claw.
Capsule finally loculicid to the base, forming a 5-rayed star.
Seeds 1-6 per cell, aril white, thin, at maturity bivalved and ejaculatory.
Distribution
Asia-Tropical, Pantropical present
Pantropical, possibly some 70 spp., in Malesia 7 spp. among which one escaped and another introduced.
Morphology
I have raised seedlings of B. dendroides of which the germination is epigaic. The first leaves, which bear successively 2, 4, 6, and more leaflets, originate from the plumule which remains between the cotyledons. Simultaneously the hypocotyl starts to lengthen, forming the initial stem carrying the leaf tuft at its apex. When this cycadoid first stage is formed, one finds below the tuft usually a collar of reflexed bristles below the leaf-scars of fallen leaves. In the annual species, characterized by a pithy (compressible) hypocotylar stem, there is usually one apical tuft, exceptionally there are two, both sessile. In the perennial ligneous species other tufts are formed, either on short-shoots or by genuine lateral distinctly sympodial branching.
The sympodial branching of the suffruticose species is very characteristic; it is partly by thick short-shoots on which the cortex is covered by leaf-scars, withering with age, and partly by long-shoots which carry always under the pseudo-umbel of leaves a reflexed tuft of hairs, the shoot itself showing no leaf-scars. In the tuft are many, often finally reflexed narrow to needle-like stipules. The peduncle of the inflorescence resembles the 'internode' of the long-shoots, but it carries on top a fascicle of narrow cuspidate bracts, the inner ones of which bear flowers.
In B. reinwardtii and B. adiantoides it may happen that in the pseudo-umbel some reduced leaves occur. This can be found also in B. fruticosum (KAUDERN 438); of this species a still more remarkable specimen has been collected at Sse Mao (PI. Yunnan & Mekong), Prince H. d'ORLEANS (in P) where the pseudo-umbel has produced a new umbel with reduced leaves and flowers, exactly similar to a normal long-shoot. This also occasionally occurs in B. reinwardtii (RANT s.n., 1922, do, 1924, BEUMEE 4848, KOORDERS 29864). A remarkable case of proliferation difficult to account for.
'Callus' of the shorter filaments. At the base of the annulus below the shorter (epipetalous) filaments there is a usually dark coloured tumidity, sometimes cup-shaped, in front of the petals. Similar ones have already been noticed in Hypseocharis by BAILLON () and in some species of Oxalis by BAILLON (1874) and PROGEL (). HALLIER f. discussed their taxonomical value as similar structures occur in Geraniaceae, Limnanthaceae and Linaceae (Beih. Bot. Centralbl. 39, ii, 1921, 165). NARAYANA (in litt.) found they have no vascular trace in B. candolleanum (called 'B. intermedium’, in ). The callosities are possibly homologous with the scales found in Dapania on the annulus at the base of the shorter filaments ().
The indument is made up of setaceous, simple hairs. In the inflorescences small, septate, capitate, glandular hairs and/or minute, red, club-shaped glands may be present.
Syst. I agree with VAN STEENIS that the subdivision of the genus as given by KNUTH is unsatisfactory and new criteria must be considered. The first provisionally proposed sect. Sensitiva (with the generic type species B. sensitivum) for annual species and sect. Prolifera (type species B. proliferum) for the suf-fructicose species. But the situation might be more complicated and a subdivision has to wait for a complete revision of the genus.
The sympodial branching of the suffruticose species is very characteristic; it is partly by thick short-shoots on which the cortex is covered by leaf-scars, withering with age, and partly by long-shoots which carry always under the pseudo-umbel of leaves a reflexed tuft of hairs, the shoot itself showing no leaf-scars. In the tuft are many, often finally reflexed narrow to needle-like stipules. The peduncle of the inflorescence resembles the 'internode' of the long-shoots, but it carries on top a fascicle of narrow cuspidate bracts, the inner ones of which bear flowers.
In B. reinwardtii and B. adiantoides it may happen that in the pseudo-umbel some reduced leaves occur. This can be found also in B. fruticosum (KAUDERN 438); of this species a still more remarkable specimen has been collected at Sse Mao (PI. Yunnan & Mekong), Prince H. d'ORLEANS (in P) where the pseudo-umbel has produced a new umbel with reduced leaves and flowers, exactly similar to a normal long-shoot. This also occasionally occurs in B. reinwardtii (RANT s.n., 1922, do, 1924, BEUMEE 4848, KOORDERS 29864). A remarkable case of proliferation difficult to account for.
'Callus' of the shorter filaments. At the base of the annulus below the shorter (epipetalous) filaments there is a usually dark coloured tumidity, sometimes cup-shaped, in front of the petals. Similar ones have already been noticed in Hypseocharis by BAILLON () and in some species of Oxalis by BAILLON (1874) and PROGEL (). HALLIER f. discussed their taxonomical value as similar structures occur in Geraniaceae, Limnanthaceae and Linaceae (Beih. Bot. Centralbl. 39, ii, 1921, 165). NARAYANA (in litt.) found they have no vascular trace in B. candolleanum (called 'B. intermedium’, in ). The callosities are possibly homologous with the scales found in Dapania on the annulus at the base of the shorter filaments ().
The indument is made up of setaceous, simple hairs. In the inflorescences small, septate, capitate, glandular hairs and/or minute, red, club-shaped glands may be present.
Syst. I agree with VAN STEENIS that the subdivision of the genus as given by KNUTH is unsatisfactory and new criteria must be considered. The first provisionally proposed sect. Sensitiva (with the generic type species B. sensitivum) for annual species and sect. Prolifera (type species B. proliferum) for the suf-fructicose species. But the situation might be more complicated and a subdivision has to wait for a complete revision of the genus.