102 ZYGOPHYLLE^. 



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 80 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 Avanting, and. even in stems of 

 about a foot in diameter it is reduced to 4 of an inch. It is of looser 

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

 Both sapwood and heartwood ow^e their tenacity to an extremely peculiar 

 zigzag arrangementi of the woody bundles. The sapwood is tastless. 

 Ihe 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 m oxalate of ealciuni 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 Yitaj of Jamaica {G. afficinale) and that of the Bahamas 

 (Cr. saiicfur/i) of which authentic specimens have been kindly placed at 

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

 iis microscopic structure.^ rt- 



Microscopic Structure— The wood consists for the most part of 

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

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

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



^LT^' n% P'*"*®"^ ^®'^«^s a^'e comparatively large but not veiy 

 LrX 1 ^^^^^^"'tructure of the sapwiod is the same as that of the 

 neart wood, but m the latter tlie ligneous cells are filled with resin. 

 iiie parenchymatous cells contain crystals of oxalate of calcium. 



thp^P^J^'^'i^^^T^^^^^^^^-The only constituent of any interest is 

 the lesin which the heartwood contains to the extent of about a four ; 



npr ir'v T ^^^ sapwood afforded us 091 and the heartwood OOO 

 per cent, of ash. 



8i7P^^^!!!f' ''^^^T''''"^ ^^'^"^ ^^"es much in estimation, according to 

 exited frn '''.I ^''•^ ^^" cylindrical form of the logs. The best i^ 

 interior of r m' ""P °* ^^^"^° Domingo, whither it is brought from the 

 ^^imio^^^^^^ , ^^^ ^"-*^^y «1-PP-^ f-- this port during 18 a 



•*^^ ions, 220 tons were exported in 1877 from Puerto Plat^i on 



out lUdy W YaleSu^^^^^^^^^ well pointed r.ea:lcanor. hist., Romae 1651, fol. ^ 



Arnauornt., m\m ^^'*''' '^'"■'^'"'" it« I'-^^ge umbels with yellow Aovvers those 



' See also Oberlin'V <a 1 1 i , of Giuaiacum officmale, the ''/ioa^^f %. 



VI. UOrfS) -i4(> and plate 



^Tliat of Gualarnm ....; ^« ?ia^. xv., 1S72. p. 3l 



apparently v^r^TCU^^^^^ ^^' '' <^^«^ribe; Guaiacuin 

 currin^r inAi.^rr. "^*^?^*- This tree, oc n« r:., ..,„ .../.,;/ 



on also 



:c1 



-Lms tree, oc aa Guayacan poMllo ; its wood is 

 3 already beon nli^^r»c+ *^,,i,,^^,i,.«-i- f^.o^.+nrA. 



an 



dez {Nova plantar n^aJ^rT?, S'™'"/ ' ^^^"^"'«^ ^'1 



. ^nuniu. et mineral meiit, Aug. 1872 



almost pulverulent fracture. parlia 



■* Consular Mcqyorts presented to i 



