A deciduous tree with ash-grey, smooth young stems. Leaves five-lobed, blades 23⁄4 to 5 in. long and about as wide; lobes triangular-ovate, acuminate, coarsely and acutely saw-toothed or lobulate, with the teeth or lobulations themselves finely serrate, lower surface with a more or less persistent covering of yellowish brown or fawn-coloured hairs; leaf stalks 24⁄5 to 34⁄5 in. long, finely downy at first. Flowers in erect, spike-like panicles of perfect and staminate flowers, main axis of inflorescence, peduncles and pedicels all hairy. Fruiting racemes about 4 in. long; fruits on pedicels 1⁄6 to 1⁄4 in. long; wings ascending, 1 to 11⁄5 long with the nutlet and about 2⁄5 in. wide.
Native of the E. Himalaya and of Upper Burma, much confused with A. acuminatum and A. pectinatum (see under these species for the marks of difference). It is generally known as “A. caudatmn” but, for the reasons explained in the note, this name must be rejected as ambiguous.
Note: The name A. caudatum starts from Wallich (Pl. As. Rar., Vol. 2, p. 4, p. 28 and t. 132 (1831)). Wallich included under it two sets of herbarium material which he had previously regarded as representing two distinct species. These he had catalogued in the East India Company’s Herbarium as A. caudatum (No. 1225) and A. pectinatum (No. 1226). In his account of A. caudatum Wallich made clear that he had come to regard this material as representing a single variable species – A. caudatum – and cited A. pectinalum as a synonym. In fact, his earlier judgement was the correct one. No. 1226 is a distinct species (A. pectinatum, q.v.); No. 1225 is, with one exception mentioned below, A. acuminatum, a species validly described by David Don some years earlier. Wallich’s description of A. caudatum is clearly compounded of these two species. As for the specimen figured under t. 132, there is nothing to match it in the Kew Herbarium, but it is nearest to a specimen of A. pectinatum in Hooker’s herbarium and is not A. caudatum as understood by Rehder (i.e. A. papilio). This confusion would have been resolved if Wallich had designated a type for A. caudatum, but he did not do so, and there is no way of deducing one from his account. Rehder, in Sargent’s Trees and Shrubs, Vol. 1, p. 163 (1905), applied the name A. caudatum Wall. to A. papilio, but excluded Wallich’s description of the staminate flowers (which refers to A. acuminatum) and the synonym A. pectinatum. But what is left of Wallich’s A. caudatum is then impossible to identify. Nor did Rehder deal with the material upon which Wallich based his account; he makes no mention of the Nos. 1225 and 1226 and the only specimen he cited for A. caudatum is one collected by J. D. Hooker in Sikkim – and the only specimen of this group in Hooker’s herbarium is A. pectinatum. It should be added that one of the collectings in the Wallich herbarium under No. 1225 seems to be A. papilio. It is sterile and mounted with a flowering specimen which is clearly A. acuminatum. Even if the sterile piece is really A. papilio, there is no reason to take it as the holotype of A. caudatum unless it be that it is the one specimen that might answer to Wallich’s descriptions of the leaves; in fact it does not agree well with his description. It will therefore be evident that the name A. caudatum Wall. has been so confused that it is best abandoned. The valid name for A. caudatum sensu Rehder is A. papilio King (Journ. As. Soc. Bengal, Vol. 65, p. 115 (1896)).