Comparative Anatomy of the Woods of the Meliaceae, Sub‐family Swietenioideae

Abstract

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...

Opening the black box: explainable deep-learning classification of wood microscopic image of endangered tree species

“…Although it had low classification accuracy, none of the Swietenia species were identified as Pterocarpus , Dalbergia , Cedrela , Carapa, or Swartzia, and the differences among these three species were small. It also confirms the conclusion that “the wood of the Swietenia species cannot be separated anatomically with any degree of certainty” [ 38 ]. For similar species of Carapa guianensis and Cedrela odorata , only two cases of test examples existed in the dataset, where Cedrela odorata was incorrectly identified as Carapa guianensis , and for these species, the model could differentiate based on the vessels.…”

Machine Learning Models with Quantitative Wood Anatomy Data Can Discriminate between Swietenia macrophylla and Swietenia mahagoni

“…In this study, SVM exhibited the highest accuracy of all the supervised classifiers with a correct threshold of over 90.0% when separating the two species (Figure 4). Machine learning models have shown considerably better performance than expert wood anatomists when separating S. macrophylla and S. mahagoni [10,11,61]. The results demonstrated in this study provide a pathway to discriminate between similar woods, including CITES species, using quantitative wood anatomy data in combination with machine learning models [36,55].…”

“…Misclassified specimens of S. humilis and S. mahagoni were typically predicted as S. macrophylla, although never in proportion with the abundance of S. macrophylla in the dataset, indicating that class imbalance in the dataset was not the proximate cause of any inaccuracy. The high wood anatomical variability within S. macrophylla encompasses much of the variability in the other two species, and even machine learning methods did not suffice to provide full forensic certainty [22,60] but did greatly exceed prior reported accuracy [10]. When separating similar species using quantitative wood anatomy data, it is recommended that a sufficiently large number of specimens be studied to ensure that the full range of variation across the species is incorporated [56].…”

“…In his 1933 paper, Panshin wrote that "the woods of the Swietenia species cannot be separated anatomically with any degree of certainty" and no publications since that time have overturned this judgment [10]. The aim of this study was to test Panshin's claim using quantitative wood anatomy data in combination with machine learning models to establish an identification method that could discriminate between three Swietenia species, namely, S. marcophylla, S. mahagoni, and S. humilis, based on a large number of specimens from wood collections.…”

A Generic Monograph of the Meliaceae

“…Moll and Janssonius (1908), Kribs (1930), Panshin (1933), andDadswell andEllis (1939) Cedrela (including Toona ) should be transferred to the subfamily Swietenioideae.…”