Intrageneric Classification Research Articles

Dalbergia Congestiflora Standl.: Wood Structure And Physico-Chemical Properties Compared With Other Central American Species Of Dalbergia

Wood structure and selected physico-chemical properties of a rare Mexican species, tentatively identified as Dalbergia congestiflora, are described and compared with other Central American species of Dalbergia. On account of their distinct wood structure, four species groups can be distinguished: 1) D. granadillo, D. hypoleuca, D. lineata and D. retusa ('cocobolo') are characterised by mainly apotracheal diffuse-inaggregates parenchyma, large and few vessels, high density (0.89-1.35 g/cm3), identical heartwood colour, and chemical composition of extractives (D. granadillo, D. retusa); 2) D. tucuruensis (including D. cubitquitzensis) and D. palo-escrito are identical in all aspects but distinct from the coco bolo group on account of differences in parenchyma distribution, heartwood colour and extractives composition (D. tucuruensis), and the consistently lower density (~0.80 g/cm3); 3) D. congestiflora and D. funera (= D. calderonii) differ markedly in heartwood colour and somewhat in heartwood extractives composition but share a high density and similar wood structural pattern characterised primarily by relatively small and frequent vessels, banded parenchyma and the presence of prismatic crystals in ray cells; 4) D. stevensonii is very similar in wood structure to D. tucuruensis but has a much higher density and different heartwood extractives composition. These results indicate that the combination of wood structure and chemistry of heartwood extractives may be successfully employed for intrageneric classification of Dalbergia.

Pollen morphology in Psychotria (Rubiaceae, Rubioideae, Psychotrieae) and its taxonomic significance. A preliminary survey

The pollen morphology in 168 species of Psychotria (Rubiaceae, Rubiodeae, Psychotrieae) has been investigated using light microscopy and, for 61 of the speices, scanning electron microscopy. Transmission electron microscopical studies have been carried out for seven of the species. Psychorria is very heterogeneoous pollen morphologically and pollen grain characteristics cannot be used for the delimination of the basis of aperture morphology, thickness of exine, size of lumina, muri, columellae and bacula, and sculpture. A key to the identificantion of the pollen types is presented and all types are issstrated. The pollen grains in Psychotria are usually 3–to 5colporte, 3‐to 5‐colpate or inapertuarate, rarely 2–4‐or 5‐porate, and have an exine that vanes widely in thickness. The sexine is reticulate, microreticulate, tectate‐perforate, rugulate or intectate, and smooth or sculptured. Exine morphology presents important characters for the taxonomic subdivision of Psychotria. Previous intrageneric classifications are in part supported by pollen morphology, but contradictions between this and other sets of charactes, such as inflorescence features. are common.

Variation in the Shrew Genus Myosorex in Southern Africa

Myosorex Gray is one of the three genera of shrews occurring in Southern Africa, the other two being Crocidura Wagler and Suncus Hemprich and Ehrenberg. The affinities of these and other African shrews have been discussed in previous papers (Meester, 1953, 1954) and a recent paper by De Balsac and Lamotte (1956) includes an extensive discussion on the intrageneric classification of Myosorex, with the description of several new forms from Central and East Africa. A taxonomic study of Myosorex has brought to light certain interesting facts concerning the nature and extent of variation in the Southern African representatives of this genus. These facts, and some speculations based on them regarding the origin and development of the species concerned form the subject matter of the present paper. The material studied consists of skins and skulls of Myosorex from a number of Southern African localities. A list...