The Fruit is a long, broad, flat pod, covered with a green velvet. It is about 12 inches long and 3 inches wide and splits with a report, the two halves curling up and the seeds being violently projected. This occurs in May and June.
Uses.—The young poles are used for local building purposes, but they are very soft and liable to attacks from white ants and borer-beetles and last only one season. Larger trees are locally cut into planks, and provide an inferior timber.
ISOBERLINIA DOKA Craib and Stapf.—Doka. LEGUMINOSAE.
This species, with its congener I. Dalzielii, is a type tree of the Tree savannah and the most common of all trees in that formation. It occurs as high-crowned forest over many hundreds of square miles of the northern provinces, though it does not extend to the extreme north. It is found in all stages according to age, from the dense covering of the cleared farm land to the 40-50 feet high-crowned forests with little undergrowth except that of its own shoots or seedlings. It grows long straight boles, usually forking at 10-15 feet, and its wide-spreading limbs form a high open crown which closes the roof of the forest. Trees in a 25 feet forest have girths of, as a rule, not more than 2-3 feet, and the crown is ¾ of the total height, and narrow, the branches ascending vertically. A girth of 5-6, or more, feet is common in trees 50 feet high. The species is very susceptible to fire and the majority of large trees have hollow centres from this cause. The stem is often a mere shell, filled with the earth of white ants or with a copious volume of reddish sap which flows out and bubbles up from the base when felled. This species seems to be more exacting as to soil conditions than I. Dalzielii, the latter predominating on higher or more stony ground, the change from one species to the other often being very marked. As a rule the species are mixed indiscriminately, especially on level country.
The Bark is dark grey with large, even-sized, rather shaggy scales. It is darker and rougher than that of I. Dalzielii. The slash is light red, the sap sticky.
The Wood is red, varying from bright red to greyish-red, with long, silvery streaks. In transverse section the pores are large, in rows, festoons and small groups, and the rays are extremely fine and close together, showing as small red bars in radial section. In the plank the pores are long, open red lines, the grain often being strikingly waved. The sapwood is silvery with a reddish tinge. The timber saws and planes well, with a smooth finish and no polish. The weight is 50-55 lbs. a cubic foot.
The Leaves are large and pinnate with an average of 7 leaflets, dark-green and shiny. The young leaves are bright red and glistening and pass through every shade from this to the ultimate brilliant green of the new mature leaf. This is most noticeable after a fire when the forest is a blaze of colour. The leaves vary very considerably in size and average some 15-18 inches, those of smaller trees being much larger.
The Flowers, which are similar in both species, are in large panicles, and each consists of 5 white, uneven-sized petals and 10 long stamens. The sepals are small, narrow and white, and the whole flower is enclosed in a hard, round, blackish-green sheath which splits into two portions in which the flower rests. They appear in February.