A revision of Haplolobus (Burseraceae)

The written history of Haplolobus is still less than one century old. O. Beccari, the great Italian naturalist, was the first to collect a specimen of this genus, June 1866 in Borneo, the only Haplolobus ever collected in W. Malesia! He, too, was apparently the first to recognize this genus as separate from Santiria, probably in 1872, but he never published it and his annotation became forgotten in his herbarium in FI (see Husson & Lam, Blumea 7, 1953. 456). The first species were described in 1889 by K. Schumann (in K. Sch. & Hollr., Fl. Kais. Wilh. Land) under Santiria. Only in 1931 the genus was split off from Santiria and formally described by H. J. Lam. The first revision appeared in 1932 (H. J. Lam, Bull. Jard. Bot. Btzg III, 12, pp. 404—419). Later revisions were by Husson & Lam (Blumea 7, 1953, 413—458; the treatment by the present author in Fl. Mal. I, 5, 1956, 238—246, was in no part original but based exclusively upon this revision) and by H. J. Lam (Blumea 9, 1958, 237—272). In 1962, after his retirement as Director of the Rijksherbarium and Professor of Systematic Botany at Leiden University, Prof. Dr. H. J. Lam intended to revise Haplolobus anew, but circumstances prevented him from doing so. The repeated and urgent requests of Prof. Lam, who was my teacher, the availability of rich new collections from New Guinea, and the possibility to study anew the types of several of the older names thought to be completely lost in B but fragments of which turned out to be still extant in the Lauterbach herbarium in WRSL, were the reasons for venturing on a fourth revision in the course of 40 years. Looking back at this 4th revision I cannot but admit that Haplolobus is doubtless an extremely difficult genus. Much more good, that is fertile material from all over its area is needed before any reasonably satisfactory and stable revision can be written. The present one is in some points probably a small step forward, notably in the better delimitation from Santiria based not only upon fruit characters but also on flower characters, thanks to which more stable geographic conclusions could be drawn. Some other deviations from its forerunners will doubtless turn out to be steps sideways or even backward. The practical difficulties are treated more in detail in the notes under H. floribundus. In the present stage of knowledge it is still impossible to say more about the taxonomic position of the genus as a whole, nor on its inner structure, than has been done by Lam (1958 and before). The taxonomic and geographic isolation of H. beccarii remains a riddle, the taxonomy of the group around and including H. floribundus remains vague, and the resemblance of some species to certain species of Santiria or even Canarium, suggesting polyphyly, remains puzzling.