264 SUMMAKY OF CUEEENT EESEAECHES EELATING TO 



Technology and Anatomy of some Silky Oak Timbers. — R. T. 

 Baker {Journ. and Proc. Royal Soc. N.S. Wales, 52, 362, 13 pis.). The 

 name Silky Oak is applied in the Australian timber-trade to a variety of 

 timbers, each having a distinct specific origin, but all possessing one 

 common character — namely, very pronounced rays, or in trade terms 

 a large silver grain — and all differing in colour, weight, hardness, and 

 anatomical structure. They all belong to the same family — Proteaceas. 

 The preponderance of the rays in the wood appears to break up the usual 

 uniformity of concentricity of annual rings into arcs on a transverse 

 section. The ray feature is so characteristic of the Proteacese that 

 it differentiates it from all other families except the Casuarinace^e. 

 Baker has made a careful histological study of five species — namely, 

 Grevillearohusta, G. HilUana, Emhothrium Wickhami, Cardwellia siihlimis, 

 and Orites excelsa. The characteristic features of each species are shown in 

 macroscopical and microscopical illustrations. The transverse sections 

 show the rays dividing the other wood-elements into segments, which 

 have their concavity outwards, towards the bark, an arrangement which 

 is found to obtain in all genera of Proteaceas except Persoonia. In no 

 other family was this found in any timbers examined. The small 

 globular bodies found in the wood-elements of the several species is a 

 unique feature ; and the arrangement of the fibres and wood-parenchyma 

 affords characters for specific determination. A. B. R, 



Mahogany and the Recognition of Some of the Different Kinds by 

 their Microscopic Characters.— Henry H. Dixon {Scientific Proc. Royal 

 Dublin Society, 1918, 15, 431-86, pis. 22-44). The mahogany of 

 commerce is derived from many different genera and species of trees. 

 A recent list included sixty-seven species as supplying timbers the 

 characteristics of which sufficiently coincide with the popular idea 

 of mahogany to be marketed as that wood. The present writer has 

 examined about forty species, of which he gives descriptions and micro- 

 photographic illustrations in the hope that they may serve as means of 

 identification. The name was originally apphed to the timber of the 

 West Indian species, Stvietenia mahagoni, and possibly also of the 

 Honduras species, S. macrophylla; but it is uncertain if any of the 

 iimliers now on the market come from ;S'. mahagoni. Dixon there- 

 fore defines as mahogany all red or red-brown timbers in which the 

 fibres of the adjacent layers cross each other obliquely, and so give 

 iir,e to a play of light and shade on longitudinal surfaces. In addition 

 a mahogany should have scattered vessels, isolated or in small mostly 

 radial groups ; the parenchyma round the vessels should be narrow and 

 inconspicuous, while the medullary rays are on the average well under 

 2 mm. in height and not more than nine cells thick. In other respects 

 the woods classed as mahoganies have very varied properties. A key is 

 given for the determination of the species by histological characters. 

 This is followed by descriptions of the elements of the wood as seen in 

 cross, transverse and radial sections, each of which is illustrated by 

 microphotography. The woods are grouped geographically as Western, 

 African, Asiatic and Australian. The majority of them belong to the 

 same family as S/cietenia, Meliacege ; but Legumnios^e supply several 

 kinds, and Dipterocarpacese, Burseracete, Urticace^e, and other families 

 are represented. A. B. R. 



