318 OBIGIKAL AETICLES. 



These do not differ in size or in other respects from the sur- 

 rounding tissue in which they appear as the representatives ot 

 vessels. In cross section the wood almost precisely resembles 

 that of Coniferae owing to the absence of ducts. Ihe me- 

 dullary rays are numerous. 





'rn 



)r=;/ 



jig 2 



fig. J. 



figS. 



Fig. 1, longitudinal. Fig. 2, transverse sections of Mulongo ' wood. 

 Fig. 3, shows irregular thickenings of the cell-wall, more highly magnified. 



— Nerium. Link, H. T. Anatomia plantarum, 1843, tab. viii. 

 l-^.—Vinca (Hber). Schacht, H. Pflanzenzelle. 217. t. 8. 



As.cij'&viKD-E.KE.—Asdepias fndicosa. B. Mirbel, Elemens de Phys. 

 Veg. tab. xi. 2. — Gynanchum, Asclepias. Mohl, H. v. Ueber d. 

 Bau * * Eanken- und Schlingpflanzen, Tubingen, 1827, § 75.-— 

 Oymnema sylvestre. Jussieu, Ad. de. Monograph des Malpi- 

 ghiacees, p. 117. Under a thick, suberous layer is a second, 

 whitish cortical zone, which projects unequal, radial plates into 

 the woody axis, lobing its contour. — Iloya carnosa. Link, H. P. 

 Icones Anat. Bot. 1837. Fasc. ii. xii. 4-5. ■ 



CoNTOLTULACEAE. Criiger, H. Bot. Zeit. 1850. p. 177. An 

 account of the structure of Argyreia speciosa, m detail. — 

 Jussieu, Ad. de. Monograph des Malpighiacees, p. 123. Convol- 

 vulus malaharicus. The wood is almost entirely composed of 

 large dotted tubes arranged in 8 or 9 concentric circles, sepa- 

 rated by as many cortical zones, which communicate with each 



