A small spreading tree with slender, glabrous branches which are greyish brown and somewhat pruinose at first, becoming reddish brown. Leaves broadly ovate in outline, 13⁄4 to 4 in. long and about as wide, cordate at the base, five-lobed; lobes triangular-ovate, tapered at the apex into tail-like points, the lateral lobes less than half as long as the central one, the two basal lobes small, spreading, dark green above, veins beneath covered with a brown wool; margins densely doubly saw-toothed. Fruiting racemes 2 to 31⁄4 in. long, soon glabrous; fruits on slender pedicels about 1⁄5 in. long, with wings spreading at a right-angle or a little wider.
Native of Upper Burma, Yunnan and Szechwan; described in 1924 by the Austrian botanist and plant explorer Handel-Mazzetti from specimens collected by him in the valley of the river Taron, a tributary of the Irrawaddy. The taxonomic boundaries of this species are unsettled and for this reason the above description is based on Handel-Mazzetti's original account. Taking all the material in the Kew Herbarium that is thought by Rehder, Fang or Murray to belong to A. taronense two distinct elements appear to be present. First, there are specimens from Szechwan originally included in A. laxiflorum var. longilobum. In these the leaf-margin is more or less sharply serrated but the teeth are not aristate; the sinuses are fairly deep; and basal lobes, though small, are discernible. The rest of the material, from farther south and west, has the lateral lobes generally more abruptly acuminate with much shallower obtuse sinuses between them and the marginal teeth bristle-tipped; basal lobes can rarely be seen.
A. taronense bears some resemblance to A. rufinerve. But the Szechwan specimens differ from that species in the relatively longer and narrower, more caudate central lobe, more acute teeth, and in having fruits with an ovate nutlet tapering into the wing (in A. rufinerve the nutlet is almost spherical and fairly sharply demarcated from the wing). The rest of the material under A. taronense is readily distinguished by the leaves being more oblong-ovate in outline and by their bristle-tipped teeth.
A. taronense was introduced to cultivation by seeds collected by Forrest on the Burma-Yunnan border in 1924 (F. 24264, distributed as “A. rufinerve”). There is a specimen under this number at Caerhays Castle, Cornwall, measuring 36 × 3 ft (1966).
From the Supplement (Vol. V)
The examples at Caerhays, Cornwall are: from Forrest 25182, 44 × 31⁄4 and 36 × 2 ft; and from F.24264, 46 × 31⁄4 ft (1975).