190 BOTANICAL GAZETTE [February 



The first part of this preliminary paper discusses the many varied properties 

 of these different woods, with regard to color, density, hardness, presence or 

 absence of year-rings, pore-rings, size and contents of vessels, distribution of 

 parenchyma, etc., and also the numerous contradictory definitions of mahogany 

 to which these structural differences have given rise. To the general public 

 and to the majority of woodworkers, mahogany is a reddish wood, generally 

 with some distinct figure and texture, and valued in proportion to the beauty 

 of its figure and the resistance of the wood to splitting and warping. Obviously 

 such a definition is not sufficient. Reddish color and figure, both emphasized 

 as distinct diagnostics of the original mahogany, Swietenia makogoni, of course 

 are essential, as also is the character described as "roeyness." According to 

 Dixon, we may recognize as mahogany "all red or red-brown timbers in which 

 the fibers of the adjacent layers cross each other obliquely, and so give rise to 

 a play of light and shade on longitudinal surfaces (' roe ') , greatly emphasizing 

 the figure and conferring on the wood a freedom from splitting and warping." 

 In addition, a mahogany should have scattered vessels, isolated or in small 

 radial groups; the circumvasal parenchyma should be thin, and the medullary 

 rays not more than 9 cells in width and under 2 mm. in height. In other 

 respects the different woods designated by this name exhibit great structural 

 variability. 



The second part of the article presents the key and well written anatomical 

 diagnoses of Western, African, Asiatic, and Australasian mahoganies. The 

 23 plates are from photomicrographs of transverse, radial, and tangential sec- 

 tions of the various woods, and are intended to show their distinct micro- 

 scopic features. — LaDema M. Langdon. 



1 



Comparative salt absorption. — Stiles and Kidd 21 have published two papers 

 on the mechanism of salt absorption by disks of carrots and of potato tubers. 

 Their method of study was to immerse a quantity of uniform disks of the 

 material in salt solutions, and follow the course of absorption by the changes 

 in the electrical conductivity. Although the conductivity is affected, not 

 only by absorption of salt, but also by exosmosis, the writers believe that the 

 latter is small, especially in the case of carrot. Potassium, sodium, and 

 calcium chlorides are readily absorbed in all concentrations from N/10 to 

 N/5000. The initial rate of absorption is roughly proportional to the con- 

 centration, but after a time this does not hold. The ratio of final internal 

 concentration (arrived at by calculation) to final external concentration they 

 call the absorption ratio. With low external concentrations this ratio is many 



21 Stiles, W., and Kidd, F., The influence of external concentration on the position 

 of the equilibrium attained in the intake of salts by plant cells. Proc. Roy. Soc. 

 B 90:448-470. 1919. 



, The comparative rate of absorption of various salts by plant tissue. 



Soc 



