Manilkara nicholsonii (Sapotaceae ), a new species from southern Natal

Manilkara nicholsonii Van Wyk, a new species from southern Natal is described. A key to the southern African Manilkara species is provided.


Introduction
Fieldwork and a comparative morphological study of the Manilkara material in NH , NU , PRE and PRU revealed an undescribed species from southern Natal. This paper provides a description and comparison with existing Manilkara species in southern Africa.
The specific epithet honours Mr. H.B. Nicholson, amateur botanist, whose extensive collecting in southern Natal has contributed considerably to our knowledge of the flora of that region.
Flowering from June to August. Ripe fruits collected during February and March.

Distribution
M. nicholsonii is found in ravine forest in southern Natal (Figure 2) . It occurs on sandy soils derived from Table Mountain sandstone and often grows among rocks on forest margins or stream banks.
Although not yet collected in Transkei, M. nicholsonii seems to be restricted to the Table Mountain

35
area of southern Natal and northern Transkei-an area particularly rich in endemic tree species . It is the only Manilkara species yet recorded from this area . Associated tree species often include endemics such as Eugenia erythrophylla Strey , E. verdoorniae Van Wyk, Pseudosalacia streyi Codd and Rhynchocalyx lawsonioides Oliv. M . nicholsonii is a rare species threatened by the large scale destruction of the few remaining patches of forest within its distribution range .

Discussion
In his treatment of the Sapotaceae for the Flora of Southern Africa, Meeuse (1963)   S. Afr. J. Bot. 1982, 1(112) of Manilkara species presently recognized in southern Africa to four . (Figure 1) seems to be most closely related toM. concolor. Vegetatively the two species can easily be confused. However, M. nicholsonii can usually be distinguished by its larger and more elliptic leaves , · e ften more acute lamina basis and characteristic woody flower galls on the branchlets (Figure 3). Similar galls (probably caused by a member of the insect family Psyllidae) have not yet been found on material from other Manilkara species in southern Africa.

M. nicholsonii
The flowers of M . nicholsonii are larger and not produced in such many-flowered fascicles as in M. concolor. In southern Africa M. nicholsonii is unique in being the only member of the Sapotaceae with the ovary glabrous. Furthermore, the fruits and seeds of M. nicholsonii are the largest of the local Manilkara species . It also differs in being the only species in which the 37 comparatively short pedicels become conspicuously thicker, woody and partly covered by periderm during the fruiting stage .
Seed characteristics are usually highly rated in the taxonomy of the Sapotaceae (Baehni 1965). It was found that the external seed morphology of the Manilkara species studied provides excellent criteria for distinguishing the species (Figure 4) . These findings confirm the results of Meeuse (1960Meeuse ( , 1963 which can be consulted for detailed descriptions of the seeds of the different species. In addition it may be noted that despite its apparent relationship with M. concolor, the shape of the cicatrix on the seeds of M. nicholsonii shows some resemblance to that of M. mochisia . In fact , the seeds of M. concolor are quite different in being only slightly compressed and without the longitudinal ridge within the cicatrix. Two slightly raised and often differently coloured areas often occur within the more elliptic or ovate cicatrix of this species.