Compilation
Saintpaulia tongwensis

USES. This taxon forms the basis of the cultivated “African Violet” industry. CONSERVATION Under the broadened circumscription of this taxon presented here, it has been collected from at least 12 sites over a broad distribution. However, the lowland sites around Tanga are known to be severely threatened by habitat degradation and it is likely that several have been lost or will be so in the near future. Populations from the Udzungwa Mts appear less threatened whilst the status of the Kiwengoma population is unconfirmed. This taxon (and the species as a whole) is provisionally assessed as Vulnerable (VU A2c) as it is estimated that more than 30% of the population has been lost in the recent past and that population decline is continuing. S. tongwensis was separated from S. ionantha on the basis of having longer fruits, paler flowers and longer, elliptic leaves with a more acute apex. Fruit length however varies considerably within this taxon and, although plants from the Tanga region assigned to S. ionantha often display the most broadly ovoid fruits, there is considerable overlap. The overall range in length:width ratio of fruits from plants assigned to S. tongwensis (2.4–4.5(–6):1) is barely different to that of those assigned to S. ionantha (1.8–3.5(–5):1). Although most commonly blue-purple, S. ionantha is known to display significant variability in flower colour (see for example Burtt, 1958: 560), including white-flowered variants. The pale violet flowers of S. tongwensis clearly fall within this range. Leaf shape is initially the most striking difference between the two taxa, largely because the most well known populations of S. ionantha from the Tanga region usually have broadly ovate leaves. However, plants from further south in the Kiwengoma Forest, otherwise largely identical to the Tanga material, have more elongate leaves approaching S. tongwensis. Plants from Sigi Falls near Tanga have elongate, elliptic leaves with notably paler lateral nerves above. The flowers are rather deep blue-purple. This population was assigned to S. intermedia by Johannson, largely on account of the shortly caulescent habit of the wild plants. However plants from this population cultivated at Kew are rosulate in habit, thus the habit of the wild plants is likely a phenotypic character. With the elongate leaves and blue-purple flowers, it appears to be intermediate between S. ionantha and S. tongwensis ;all three entities are here considered to belong to a single variable taxon. Plants from the Udzungwa Mts (T7), at or near Sanje Falls, growing in lowland rainforest appear very close to this taxon. Photographs of fruiting material recently collected there (W.R.Q. Luke, pers. comm.) clearly place it within the subsp. ionantha - subsp. pendula group, the fruits being squat and ovoid. The first collection from this region (Sanje Falls, Polhill & Lovett 5130!) has spreading hairs on the leaves and petioles and is largely inseparable from subsp. ionantha. However, a later collection (Sanje–Mwanihana route, P.A. & W.R.Q. Luke 5004!) has ascending hairs on the petiole, thus likely having similarly angled hairs on the upper leaf surface. This would tend to place that specimen closer to subsp. pendula, yet the obscurely serrate margin and obtuse apex to the leaves are consistent with subsp. ionantha. This material is therefore provisionally placed in the latter but requires further investigation. The cultivated material at R.B.G. Kew labelled as originating from the Polhill & Lovett collection (accession number 1983-8132) is clearly different to the herbarium specimen of the wild material and is believed to have been mislabelled (it is referable to subsp. pendula).