Indumentum

Indumentum

All species, except the hairy B. bullatum , appear to be glabrous, but high magnification shows that they all possess very small lepidote hairs (called minute stellate hairs by Radcliffe-Smith 2001). In many descriptions these were overlooked. Young parts of the plant are totally covered with these small, yellow to orange lepidote hairs and, as a result, may even have an orange glow. Probably, the lepidote hairs have a secretory function as some specimen labels indicate stickiness and young parts may look lacquered when dry (or seem to have a layer of glue after dehydrating with boiling water). The hairs disappear with age, but on buds, fruits and in the axils of adult leaves the hairs are more resistant, though on the bark they become obscured by the formation of secondary bark, lenticels and often by fungal infections (probably due to the sweet secretion).