102 ZYGOPHYLLEJE. 



number of circles resembling annual rings, the general form of which is 

 evident, though the individual rings are by no means well defined. 

 More than 20 such rings may be counted in the sapwood of a log such 

 as we have mentioned, and more than 30 in the heartwood. The pith- 

 less centre is usually out of the axis. The medullary rays are not 

 visible to the naked eye, but may be seen by a lens to be very numerous 

 and equidistant. The pores of the heartwood may be distinguished as 

 containing a brownish resin, while those of the outermost layer of sap- 

 wood are empty. 



In the thickest pieces sapwood is wanting, and even in stems of 

 about a foot in diameter it is reduced to i- of an inch. It is of looser 

 texture than the heartwood and floats on water, whereas the latter sinks. 

 Both sapwood and heartwood owe their tenacity to an extremely peculiar 

 zigzag arrangement^ of the woody bundles. The sapwood is tastless. 

 The heartwood has a faintly aromatic and slightly irritating taste, and 

 when heated or rubbed emits a weak agreeable odour. 



The bark which was formerly officinal but is now almost obsolete, 

 is very rich in oxalate of calcium and affords upon incineration not less 

 than 23 per cent, of ash. It contains a resin distinct from that of the 

 wood, and also a bitter acrid principle.^ 



The Lignum Vitse of Jamaica {G. officinale) and that of the Bahamas 

 {G. sanctum), of which authentic specimens have been kindly placed at 

 our disposal by Mr. G. Shadbolt, display the same appearance as well 

 as microscopic structure.^ 



Microscopic Structure — The wood consists for the most part of 

 pointed, not very long, ligneous cells (libriform), traversed by one-celled 

 rows of medullary rays. There are also thin layers of parenchymatous 

 tissue, to which the zones apparent in a transverse section of the drug 

 are due. The pitted vessels are comparatively large but not very 

 numerous. The structure of the sapwood is the same as that of the 

 heartwood, but in the latter the lig-neous cells are filled with resin. 

 The parenchymatous cells contain crystals of oxalate of calcium. 



Chemical Composition — The only constituent of any interest is 

 the resin which the heartwood contains to the extent of about a fourth 

 of its weight. The sapwood afibrded us 0'91 and the heartwood 060 

 per cent, of ash. 



Commerce — Lignum Vitas varies much in estimation, according to 

 size, soundness, and the cylindrical form of the logs. The best is 

 exported from the city of Santo Domingo, whither it is brought from the 

 interior of the island. The quantity shipped from this port during 1871 

 was 1494 tons;^ 220 tons were exported in 1877 from Puerto Plata on 



1 It has been remarkably well pointed mexicanor. hint., Romae 1651, fol. 63) 



out already by Valerius Cordus {obiit 1544). imder the name of Gauyacan. He mentions 



See Gesner's edition of his Hist. Stirpium its largo umbels with yellow flowers, those 



Arfjejitornt., 1561. 191. of Guaiacum officinale, the " i/oaxacreH " or 



'^ See also Oberlin et Schlagdenhauffen, Lignum sanctum, being blue. In the Pro- 



Journ. de Pharm. 28 (1878) 246 and plate dromus FloroR Neo-Granatenti8(Ann.Sdenc. 



vi. nat. XV., 1872. p. 361) J. E. Planchon also 



3 That of Guaiacum arhoreum DC. is describes Guaiacum arboreum, known there 



apparently very different. This tree, oc- as Guayacan polvillo ; its wood is of an 



earring in New Granada, has already been almost pulverulent fracture, 

 noticed (1571— 1577) by Francisco Heman- ^ Comtdar Reports presented to Parlia- 



doz [Nova 2>lantarum, animal, et minernl. ment, Aug. 1872. 



