ECOLOGICAL AND SYSTEMATIC WOOD ANATOMY OF ALSTONIA (APOCYNACEAE)

The wood anatomy is described of three sections of the genus Alstonia: sections Alstonia, Monuraspermum, and Dissuraspermum. The wood anatom ical characters support the infrageneric classification on the basis o f macropmorphological and pollen morphological features (Sidiyasa 1998 ). Vessel frequency, mean tangential vessel diameter, L/D ratio, ray f requency, presence or absence of laticifers, parenchyma distribution, fibre wall thickness, and fibre wall pitting are all, in various degre es, diagnostic to separate the light Alstonia timber group (= section Alstonia) from the heavy Alstonia group (including the other two secti ons studied). Sections Monuraspermum and Dissuraspermum can be separat ed on vessel frequency and mean tangential vessel diameter. Among the light Alstonia group, the swamp inhabiting species have lower multiser iate rays than the non-swamp species which presumably root in well-aer ated soils. Vessel elements and fibres also tend to be shorter in mate rial from swamps, but this difference is not statistically significant . This tendency is perhaps associated with the physiological drought i nduced by water-logged soils.