286 BLAKE: REVISION OF MAHOGANIES 



Observers 



The different observers apparently did not all set alike, but 

 each was able to repeat his own measurements with sufficient 

 precision so that each could have measured a pressure difference 

 to ^o.ooi inch or about ±0.02 mm. 



The above-mentioned use is but one of the many to which such 

 a useful little instrument can be put and no doubt specially 

 shaped heads could be obtained for particular purposes if desired. 



BOTANY. — Revision of the true mahoganies {Swietenia). vS. F. 

 Blake, Bureau of Plant Industry.^ 



The genus Swietenia, from which the true mahogany of com- 

 merce is derived, was described by Jacquin- in 1760. His single 

 species, Swietenia mahagoni, was based on a reference to plate 

 81 of the second volume of Catesby's Natural History of Caro- 

 lina. This plate is also the basis of Linnaeus' Cedrela mahagoni,^ 



^ Received March 12, 1920. 

 ^ Enum. PI. Carib. 4: 1760. 

 * Syst. ed. 10. 940. 1759. 



