TEREBIXTIIA CKJ2. 203 



in most of tlioir organs, it may be said that tliey are met with 

 especially iu the bark. This in Balsumca^^ for instance, possesses a 

 liber zone plunged in the middle of a cellular tissue full of gummy 

 resinous matter. There is also some in the pith. This matter may 

 even ooze out, the first year, by slits in the epidermis and the 

 cork. But later, as is seen in B. Mjjrrha^ " the production of balm 

 cannot take place in the herbaceous layers of preceding years, for 

 every year it makes an exfoliation throwing back the layers pre- 

 vioiisly formed." Every where where there is any living parenchyma 

 the resinous substance may be produced. The exfoliation of the ex- 

 terior layers of the cortical parenchyma has been followed in the B. 

 Africana which gives hdellium ; it is produced in fragments. In the 

 BoswclUa papyrifera^ on the contrary, it is produced by large parch- 

 ment-like plates giving to the trunk of this tree the same appearance as 

 that of the Birch.'- In the Pliytocrcnccv the organisation of the stems 

 is quite exceptional; it has been compared to that of the Meni- 

 spcrmacem and Bignoniacecc. In Phijtocrcne, Griffith ^ has pointed 

 out what he calls enormous medullar}'' rays, arranged symmetrically, 

 very thick and equally spaced (nine in number in a young stem of 

 P. (jhjantca). They are composed of elongated cells, attenuated at 

 the summit crossed by striped ducts. The wood is very porous, 

 formed of numerous large tubules, pierced with slits plunged in its 

 punctate prosenchyma. There are distinct concentric zones in the 

 Avood, each having their rays independent of those of the neighbour- 

 ing zone. The thick radiated lines, considered by Griffith to be 

 medullary rays, have been regarded '■' as belonging to the woody sys- 

 tem, and as forming the interior portion of a second ring of wood 

 developed outside the fii'st."' In the Phijtncrcncw^ as in the Mappiecc^ 

 the phenomena of being drawn up which show themselves so fre- 

 (|uently in the leaves, and especially in the lateral branches, cause in 

 consequence, at certain levels, a transverse section to show not only 



' SIarch. in Adansonia, vii. 261, t. 8. * For the anat. of Phytocroie, see also : Grii'f. 



■ The same author has obticrved an analogous Nulul. iv. 324. — Tueviu. in But. Ztit. (1847), 



arrangement of the halsamic substance, not 400; in. Ami. Nat. Hist. acT. 2, i. 131. — Lixul. 



only in the stems of Pistacin, but also iu eertain Iidrod. i. 21 1, fif,'. ; Vvg. Eiiiyd. 271. — H. Mohl. 



galls of P. Teiebiiithus {Aiiacaid. 1.52, t. 3). in Jlol. Zcit. (1855).— JIetten. Bcitr. z. Hot. 



» In Wall. PL As. Jlu,: iii. U, t. 216; Icmi. (1850), 60. 



cccxo. — IvADi.K. in Floia (1858), 206. — Oliv. •■' On the structure of the branches of Gri- 



Stem, in llicut. 29. sul/ta, see II. B.n. in Adansoiiia, iv. 213. 



* A. Ju.-s. Monnijr. Malpv/Iiiac. 122. 



