Dec., 19331 PANSHIN -SWIETENIOIDEAE THE MAHOGANY FAMILY (MELIACEAE)The Mahogany family consists of 40 genera and about 800 species of trees, shrubs, or rarely woody herbs, widely distributed in the tropical and sub-tropical regions of both hemispheres, a few species extending into the temperate zones. Meliaceous plants are characterized by alternate or occasionally opposite, pinnately compound (rarely palmately compound or simple) leaves with opposite or alternate, usually entire leaflets; regular, perfect, or polygamo-dioecious flowers in axillary or terminal panicles, racemes, spikes, or occasionally in umbels; and capsular, baccate, or drupaceous fruits, the first bearing winged or unwinged seeds.The woods of this family range through shades of red, reddish-brown, or. less frequently chocolate-brown or white, and exhibit all degrees of sheen from lustrous to dull. The weight and hardness likewise vary between wide extremes; the genus Cedrela, for example, includes a number of very soft, light woods with specific gravities between 0.30 and 0.65, while the other extreme is represented by the hard and heavy woods of Soymida species which, when oven-dry, will usually sink in water (Sp. Gr. 1.0-1.2). Some of these woods are pleasantly scented, relatively few (such as the Onionwood of Australia, Owenia cepidora F. Muel.) , have unusual aromas, while many others are devoid of odor or rapidly lose their scent when exposed to the air. The grain and texture also exhibit wide variation, but there is a decided tendency toward interlocking of the grain, with corresponding ribbon and roey figures in quarter-sawn lumber. Growth rings are frequently distinguishable, but most of the woods are of the diffuse porous type; in fact, ring porous woods are found in only two genera. The vessels range from very small to large and occur either solitary or in short radial groups, rarely in small nests; they generally contain copious deposits of reddish-brown or black gum, and in some instances chalky inclusions are also present; the vessel perforations are simple throughout, and the inter-vessel pits are mostly small and often with confluent apertures. The fibers are usually fine and thinwalled, and are often septate and gelatinous. Parenchyma is relatively abundant around the vessels, and zonate and metatracheal parenchyma in varying amounts are not infrequently present. The rays may be either very narrow and indistinct in the transverse section or comparatively wide and visible with the naked eye; they vary in width from I to 10 cells, and are either. of the homogeneous type or decidedly heterogeneous. Ripple marks feature a few of these woods. Lysigenous gum canals, possibly of traumatic origin, are present in many cases.The economic importance of the Meliaceae centers primarily on timber production, since many offhese trees produce valuable ornamental woods sought by the trade, among which the following deserve mention: genuine Mahogany from Sioietenia spp.; Spanish Cedar, the product of Cedrela odorata Linn.; the Toon of India from...
