Psychotria geophylax Cheek & Sonké

Cheek, M., & Sonké, B. (2005). Two Further New Species of Psychotria (Rubiaceae) from Western Cameroon. Kew Bulletin, 60(2), 293-300. Retrieved from http://www.jstor.org/stable/4110940

Type

Cameroon, South West Province, Mt Kupe, Nyasoso, c. 1190 m, fl., fr. 26 Oct. 1995, Sidwell 416 (holotypus K!, isotypi BR!, MO!, P!, SCA, WAG!, YA).

Morphology General Habit

Shrub 2 - 5(- 6) m tall

Morphology Stem

Stems 4- 6 mm diam., drying mid to dark brown, matt, glabrous

Morphology Leaves

Leaf-blade membranous to thinly chartaceous, lacking bacterial nodules, drying matt dark brown above and below, obovate or elliptic, (13.5 -)17.5 - 31 x 8 - 12.5(- 13.7) cm, apex shortly acuminate, acumen (0.2 -)0.3 - 0.6(- 0.7) x 0.2 - 0.3 cm, base acute-decurrent, midrib and secondary nerves prominent below, very slightly prominent above, midrib usually with a shallow longitudinal groove on the upper surface, secondary nerves (10 -) 12 - 14(- 17) on each side of the midrib, arising patent to the midrib, and arching abruptly upwards towards the margin, then forming an acute angle to the midrib of c. 45 degrees, brochidodromous, terminal junction of the secondary nerves about 0.7 cm from the margin, with a parallel but weaker marginal nerve 0.15 - 0.3 cm from the margin, glabrous

Morphology Leaves Petiole

Petiole plano-convex in transverse section, (1.5 -)2.5 - 4(- 4.8) cm long, 0.15 - 25 cm deep, 0.2 - 0.3 cm wide, glabrous, lower surface usually with conspicuous randomly orientated white raphides c. 0.1 mm long

Morphology Leaves Stipules

Stipules ovate or elliptic, free, green when live, 18 - 35 x 15 - 20 mm on stem below inflorescence, to c. 13 mm long on subsidiary stems, persisting for two nodes below the inflorescence, apex slightly acuminate or acute, entire or bifid by up to 4 mm, outer surface glabrous, but with longitudinally arranged raphides c. 0.3 mm long, venation inconspicuous, inner surface densely papillate to appressed hairy with translucent colleters up to 0.4 mm long, often conspicuous at the distal margin

Morphology Reproductive morphology Inflorescences

Inflorescence sessile, densely capitate, 3 - 4.5 cm diam., c. 500-flowered, only 2 - 3 of which are at anthesis at one time, peduncle and rachis highly reduced, inconspicuous

Morphology Reproductive morphology Inflorescences Peduncles

Partial peduncles 30 - 50, arranged in an umbel, each terete, c. 5 x 1.5 mm, bearing c. 10 flowers at the apex, flowers single or grouped in dichasial cymes, the 2 - 5-flowered subsidiary branches each 0 - 2 mm long

Morphology Reproductive morphology Inflorescences Bracts

Bracts sheathing the subsidiary branches, irregularly coarsely laciniate, c. 2 mm long, densely appressed hairy on both surfaces; pedicels c. 1 mm long, confluent with the calyx

Morphology Reproductive morphology Flowers

Flowers hermaphrodite, 5-merous, heterostylous Short- styled flowers as the long-styled, but corolla tube c. 6 mm long; stamens exserted by c. 4 mm; free filaments c. 4 mm long, inserted c. 2 mm from the mouth of the tube; style c. 6 mm long, the stigma just exserted from the mouth

Morphology Reproductive morphology Flowers Calyx

Calyx matt brown, subcylindrical, c. 13 x 3 mm long; free part c. 10 mm long, tubular part ovoid, 4 mm long, lobes oblong-ligulate, 6 x 1.5 mm, apex rounded, inner surface glabrous, raphides conspicuous, outer surface with grey-brown patent hairs c. 0.2 mm long

Morphology Reproductive morphology Flowers Corolla

Long-styled flowers: Corolla dull orange, c. 13 x 3.5 mm; tube 7 mm long, 3.5 mm wide, widest near the apex, inner surface glabrous apart from a ring of hairs at the level of insertion of the filaments on the inner surface, a few hairs extending to the mouth of tube, outer surface with the same indumentum as outer calyx, lobes valvate, thick, reflexed at anthesis, oblong-ovate, c. 4 x 2 mm, dorsal appendages absent

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens with free filaments absent or very short, inserted c. 3 mm below the mouth of the tube, anthers just included, c. 3 x 0.7 mm

Morphology Reproductive morphology Flowers Gynoecium Style

Style exserted, 11 - 13 x 0.2 mm, glabrous, stigmatic lobes divergent, c. 0.5 mm long; disk enfolding base of style, globose, slightly 4-lobed, 1.25 mm diam., glabrous

Morphology Reproductive morphology Fruits Infructescences

Infructescence a globose 10 - 50- fruited cluster c. 6 cm diam.; peduncle c. 3 mm long, bearing several stout partial-peduncles 5 - 10 mm long; bract remnants persistent; pedicels stout, 5 mm long

Morphology Reproductive morphology Fruits

Fruit leathery, dull orange, ovoid, (15 -)17- 25 x 7- 10(- 15) mm including the calyx, smooth, when live, when dry with several thick longitudinal ridges; crowned by the persistent, foliaceous calyx; pyrenes (1 -) 2, lacking preformed germination slits, pulp adhering, cartilaginous

Morphology Reproductive morphology Seeds

Seeds (1 -)2, dorsal surface with c. 5 well-marked, broad longitudinal ridges, ventral surface smooth, without ridges, with c. 5 invaginations; endosperm with c. 10 invaginations.

Distribution

Cameroon, SW Province, Mt Cameroon, Mt Kupe and the Bakossi Mts.

Ecology

Lowland to submontane evergreen forest; (300 -)700 - 1500(- 1600) m alt.

Note

Derived from the Greek, meaning "Earthwatch", commemorating the organisation that has supported botanical fieldwork for conservation purposes in South West Province, Cameroon during the period 1993 - 2004. The taxonomic affinities of Psychotria geophylax seem to lie within sect. Flaviflorae E. M. A.Petit, given that it keys out in Petit (1964) to a species in this section (P. dorotheae), and that it resembles another species in that section (P. gabonica). Psychotria geophylax fits several of the characters that, according to Petit, define the section: the usually entire, ovate-triangular stipules, the presence of small bracts in the inflorescence, the abaxial and adaxial faces of the endosperm ruminate and the yellow flowers (orange in P. geophylax). However, several features of P. geophylax do not agree with the sectional description: the capitate inflorescence (not paniculate), and the ridged seeds (not smooth). Both of these discordant characters do occur in P. dorotheae, which Petit placed next to P. gabonica. Psychotria gabonica has a subcapitate (congested paniculate) inflorescence. The affinities of P. geophylax therefore seem closest with these two species. Despite these evident affinities, P. geophylax is easily distinguished from both by the large leaves and the extremely long calyx limb. Generally, in sect. Flaviflorae the calyx limb is extremely short (including P. gabonica and P. dorotheae), or absent. In only one or two species do the longest lobes reach 1 - 2 mm, whereas in P. geophylax they attain 6 mm long. Although in Hepper (1963) Psychotria geophylax keys out as P. psychotrioides, there seems little taxonomic affinity between the two. The latter species is unusual in having two caducous bracts that enclose the inflorescence, has white corollas, and seeds that lack ridges, and lack invaginations on the dorsal face. Petit (1964) treated P. psychotrioides as of uncertain sectional position, stating that the species is not close to another.

Conservation

Although 23 specimens are recorded (above) of Psychotria geophylax, it is only known from eight localities, at several of which (e.g. Bakolle Bakossi and Mt Etinde) its forest habitat is believed to be threatened with clearance for agriculture. Accordingly we here assess this taxon as VU B2a,b(iii), using the criteria of IUCN (2001). Local populations of this species appear to vary greatly in the numbers of individuals. In comparing two sites which have received broadly similar levels of collecting activity, Mt Etinde and Nyasoso, it is noteworthy that whereas only two specimens are recorded at the first, eleven are known at the second. Within the Kupe-Bakossi area, the stronghold of this species, the distribution of P. geophylax is extremely patchy. Although it is evidently common above Nyasoso, it has not been recorded at all at other sites in the area, such as Kodmin, Ngomboku and Muambong, which have also been subjected to fairly intensive botanical survey by the same set of collectors. Since the species appears to be fertile most of the year (it has been collected in every month bar April, September and December, usually with fruit), this cannot be attributed to collections at these sites being at times inappropriate to record presence of the species, but rather to real absences. Consequently it is possible to be fairly precise about the distribution of the species: it is known only from the western and southern slopes of Mt Kupe, where it is common, and from the western foothills of the Bakossi Mts where it is rarer, and from Mt Etinde at Mt Cameroon, where it is scarcer still.