The genus Tetradenia Benth . ( Lamiaceae ) . I . African species

The genus Iboza N. E. Br. is placed as a synonym of Tetradenia Benth. and the following new combinations are made: T. barberae (N.E. Br.) Codd, T. brevispicata (N .E. Br.) Codd and T. riparia (Hochst.) Codd.


INTRODUCTION
During studies in Lamiaceae for the Flora of Southern Africa it became apparent that the African genus Iboza N.E.Br. (1910), in which five species were originally upheld, is not generically distinct from Tetradenia Benth.( 1830), based on a single species from the Malagasy Republic.A comparison of the two genera was facilitated by the fact that both male and female plants of a Tetradenia were collected by Mr D. S. Hardy and Prof. W. Rauh during their visit to the Malagasy Republic in 1969 and have flowered regularly in winter in the PRE nursery.
As well as all having a similar facies and inflorescence structure, with very small, dioecious flowers, the species now included in Tetradenia have a characteristic floral pattern (see Figs 2,4 & 6): (c) in the male flowers there is a non-functional ovary (though T. barberae may be an exception in this regard) and 4 shortly exserted somewhat spreading stamens, 2 of which are ascending on each side of the upper lobe and 2 descending on each side of the lower lobe.(d) in the female flowers there are no signs of stamens or staminodes and the style is relatively deeply bifid.(e) the disc is produced into 1 or 2 conspicuous lobes which exceed the ovary in height (apparent also in male flowers).
(f) There are small gland-like structures at the nodes (2 below each petiole) which have not been observed in any other genus in the Lamiaceae, but which are present in all the species now included in Tetradenia (Fig. 1).(a) the calyx is divided nearly to the base below and consists of an upper ovate lobe and two lateral oblong lobes which are emarginate or bifid.
(b) the corolla limb is somewhat spreading and 4-lobed, with the upper lobe bifid or bilobed (sometimes giving the superficial appearance of a 5-lobed corolla), with 2 oblong lateral lobes and an oblong, slightly concave lower lobe which is slightly longer than the other three.

TETRADENIA
florai characters are very similar in all the riparia (Hochst.)N.E.Br. ( -Moschosma riparia species and are not of much diagnostic value.In the Hochst.) maje f]owers a small infertile ovary develops Moschosma Auct., non Reichb.
(occasionally fertile in T. barberae), whereas in Perennial shrublets, soft shrubs or small trees, female thuere areu n° s j S ns, of stan;ens °r usually leafless or nearly so at flowering stage; stems staminodes.Bentham, who had only a single male brittle or semisucculent, at first softly glandular-specimen when he described T. fnmcosa, gave the pubescent and somewhat quadrangular, glabrescent impression that the flowers were functionally and terete with age.Leaves small or large, those ermaphrodite.subtending inflorescence branches or secondary The structure of the calyx is basically the same in branches smaller towards the apex, often semisuccu-all species, but shows some variation in the degree of lent, variously pubescent, crenate-dentate, aroma-toothing of the laterial lobes.This is best seen in the tic.Inflorescence paniculate, terminal and on lateral female flowers where the calyx enlarges somewhat branches, often diffusely branched, the ultimate when in fruit.branches spike-like (referred to as 'flower-spikes'); The corolJa tube tends tQ be in bracts small, ovate-deltoid to broadly ovate, male flowers and smaller and more tubular in female imbricate in the bud stage, caducous or semipersis-flowers, and there is some variation between species tent Flowers dioecious or occasionally bisexual IT.
in the , , h of the tube The sli htl asymmetric barberae), in whorls of 4 -1 0 , sessile or shortly limb of 4 lobes (the upper lobe being emarginate or pedicellate, dense or lax, mauve or whitish.Calyx bifld produce the effect of a 5-lobed limb) is minute, campanulate, 3-lobed, divided nearly to the much the same in male and female flowers of all base below, the upper lobe ovate, lateral lobes species, with the low'est lobe longer than the others oblong, bifid or emarginate; in female flowers the and usua|| shanow|y concave.calyx enlarges at maturity and the upper lobe becomes erect.Corolla small, tubular or funnel-Bentham drew attention to the similarity between shaped; limb spreading, asymmetrical, 4-lobed, ^is species and Moschosma riparia Hochst.but kept lobes oblong, rounded, the upper lobe emarginate them in separate genera on the basis of the greater or bifid, the lowest lobe usually the longest, flat or development of the disc in T. fruticosa.It appears slightly concave.Stamens 4, free, erect or spreading, *n ^ f m ticosa the disc is purple-coloured and absent in female flowers.Disc 1-or 2-lobed.Ovary 2-lobed whereas in the African species it is present but usually infertile in male flowers (1 or 2 colourless and usually 1-lobed.The lobes exceed the seeds per male flower occasionally found in T. ovary in height.barberae); style exserted, deeply bilobed in female flowers.Nutlets oblong-triquetrous.
When N. E. Brown described Iboza, he correctly ., ._ , r .separated it from Basilicum Moench (= Moschosma Three species are recognized in Southern Africa, Reichb.) on the dioecious flowers and the entirely one of which, T. riparia, is very variable and extends different calyx and corolla, but overlooked the to Angola and through east tropical Africa to little-kown Tetradenia Benth., possibly because the Ethiopia, in addition to the type species, T.
description implied that the flowers were hermafruticosa, two further species from the Malagasy phrodite Republic were described by Briquet, but no material of these two species has been seen and so they are All the indigenous species are used medicinally by omitted from the present treatment.They will be native tribes in the treatment of colds and chest dealt with in a subsequent article. complaints.
Disc with 1 lobe developed beyond the infertile ovary.Style exserted, shortly bifid.Female flowers not seen, but occasional seeds are formed in the male flowers (Fig. 2).
A xerophytic shrublet of karroid Fish River scrub.The type specimen was recorded from the 'Orange River Colony', but this may be an error.The only other two gatherings seen were collected at the same time, in March 1966, as shown below.Evidenly a rare and distinct species, widely separated from other members of the genus.It is characterized by the uniform short dense tomentum on all parts, lacking stipitate glands and long multicellular hairs, the sparsely branched male inflorescence with relatively long, dense flowerspikes, the small ovate prominently nerved leaves which are present at flowering time, and the deeply toothed lateral calyx lobes, giving the calyx a 5-toothed appearance.The fact that 1 or 2 seeds per flower are occasionally formed in what appear to be essentially male flowers requires further study in the field.The species may be transitional between the hermaphrodite and dioecious condition.The pre sence of seeds can be detected by a slight increase in the size of the calyx after flowering.

2.
Tetradenia brevispicata (TV.E. Br.) Codd, comb.nov.Twiggy shrub or small tree 0,6-2 ( -3 ) m tall; stems slender, woody terete, greyish-black, at first finely glandular-tomentellous, lacking stipitate glands or long multicellular hairs.Leaves rather small ovate-rotund to rotund, 12-30 (-5 5 ) x 10-30 (-5 0 ) mm. finely glandular-scabrous above, densely glandular-tomentellous beneath, the lower surface being obscured by a short cobwebby tomentum lacking stipitate glands, the nerves often fairly prominent; apex rounded, base rounded to subcordate, margin crenate to deeply crenate-dentate; petiole 4 -1 5 mm long.Inflorescence appearing after most of the leaves are shed, consisting of spikes or small panicles borne terminally and in the axils of the upper leaves, often for some distance along the stem; male and female flower-spikes dense, the male 10-20 (-2 5 ) mm long, the female shorter; rhachis densely glandular-hispidulous; bracts broadly ovate, acute, 1,5-1,75 x 1,5 -2 mm, shortly tomentellous and gland-dotted, caducous; verticils usually 6flowered; pedicels 0,5 mm long.The species is characterized by the slender, twiggy stems with greyish-black bark, the relatively small roundish deeply crenate-dentate leaves with a fine dense tomentum on the under-surface, and the short dense male flower-spikes.The flowering period is mainly from June to September when the plants are leafless.It was first collected by Rehmann at W onderboompoort in N ovem ber-D ecem ber 1879 but his specimens lacked flowers and were included in Plectranthus grandidentatus by Giirke (Codd in Bothalia 11: 397, 1975  Soft shrub or small tree 1 -3 ( -5 ) m tall, freely branched; stems semisucculent, brittle, rather stout, at first 4-angled and glandular-pubescent, becoming terete and glabrous with age; bark pale brown.Leaves petiolate; blade ovate-oblong to rotund, 3 5-80 (-1 0 0 ) x 3 5-70 (-9 0 ) mm, sparsely to densely glandular-pubescent on both surfaces, on the upper-surface usually shorter and more scabrid, on the under-surface mainly restricted to the veins or stipitate-glandular to densely white tomentose over the whole surface, veins often prominent below, apex rounded, base rounded or truncate to cordate, margin coarsely crenate to crenate-dentate; petiole up to 40 mm long, densely glandular-pubescent.Inflorescence a terminal, usually large panicle, diffusely branched and up to 300 x 200 mm in male specimens, smaller and more compact in the female, appearing usually after the leaves are shed; inflorescence branches subtended by leaves beco ming smaller towards the apex; male flower spikes dense to lax, 20-80 mm long; female flower-spikes dense, 10-25 mm long; rhachis densely glandularpubescent; bracts broadly ovate, 1 ,5 -2 x 2 -2 ,5 mm, densely glandular-hispidulous, caducous; verti cils 4 -8 (usually 6)-flowered; pedicels 0 -0 ,5 mm long.Calyx 1 mm long, densely glandularhispidulous, expanding in female flowers to 2,5 mm.Corolla white to mauve, pubescent without; in the male 3-3,5 mm long, tube funnel-shaped; in the female 2-2,5 mm long, tube tubular-funnel-shaped.Stamens exserted.Disc colourless, 1-lobed.Style exserted by 1 mm; style branches 0,4 mm long in female flowers, shorter in male flowers.Nutlets oblong, pale brown, 0,6 mm long (Figs 5 & 6).Occurs in Southern Africa from coastal Natal to Swaziland, Transvaal, south-eastern Botswana and the northern half of South West Africa/Namibia, extending to Angola and through Mozambique, Zimbabwe and Zambia to Malawi, Tanzania, Kenya, Uganda, Sudan and Ethiopia.A selection of specimens from Southern Africa (usually one per degree square) is given below.A good deal of variation is included in the present concept of T. riparia but no pattern emerges and so infraspecific taxa are not upheld.In the typical form the under-surface of the leaf is thinly pubescent, with longish appressed hairs mainly on the veins.In the type of Iboza bainesii there is a dense white cobwebby tomentum which completely obscures the under-surface.There are, however, intermediate forms, often with numerous stipitate glands in addition to the multicellular hairs and sessile gland-dots.These are found in South West Africa/Namibia and the Transvaal, but in both territories specimens with sparse pubescence are found.The leaf-base varies from cordate to truncate or rounded independently of the degree of tomentum.
In the tropical African specimens seen there seems to be a possible link between sparse under-side leaf pubescence, lax male flower-spikes and mauve corolla on the one hand, as against densely tomentose under-side of the leaf, fairly dense male flower-spikes and whitish corolla on the other.However, most specimens either lack leaves, lack notes on corolla colour or have female flowers, and there appear to be intermediates.Also, there seems to be no association between these characters and geographic distribution.Extensive field obser vations are required to ascertain if the complex can be subdivided into meaningful groups.
Because of its strongly aromatic leaves, it is sometimes referred to as Ginger-bush.