OLIVEK ON THE STEM OF DICOTYLEDONS. 303 



Scliultz, C. H. Die Cyklose. Nova Acta, 1841, xviii. Suppl. ii. 

 tab. xvii. 1, 2. 



CEUCiFEEiE. Hartig, Th. Bot. Zeit. 1859, 109. Araiis alhida. 

 — Hanstein, J. iiber den Bau des Dicotylen Holzringes. 

 Pringsheim's Jalu'b. i. 231, with figures. Conuection of arrange- 

 ment of the leaves with the wood- formation. 



Eesedaceae. — Reseda lutea. Mueller, J. Monographie de la 

 Famille des Besedacees. Zurich, 1857. Anatomic, p. 16, tab. 1.- 

 The wood- zone consists of thick- walled prosenchyma traversed oy 

 wide dotted vessels and some much elongated parenchymatous 

 cells which are found in the immediate neighbourhood of the 

 vessels. The medullary rays are complete, narrow, and tolerably 

 numerous. The liber cells are very thick-walled, long, and col- 

 lected usually in groups of 3 to 7. 



BiXACEAE. — Bixa Orellana. Medullary rays are numerous and 

 narrow. The wood consists of elongated cells, not much thick- 

 ened and often with abrupt terminations, traversed by very 

 minutely dotted or slit-marked vessels, usually two or three 

 together radially. (D. O.) 



PoLTGALACEiE. — Securidaca erecta? J. Decaisne. Sur les Lardi- 

 zabalees. Arch, du Museum, 1839, i. 205. Eemarkable from 

 the curvature and ii^egularity of its wood-zones, is figured (PL x.) 

 Destitute of medullary rays. No liber was observed. — Criiger, H. 

 Bot, Zeit. 1850, op. cit. IGl. An account of the structure, with 

 figures, of Securidaca voluhilis. Catacoma lucida, p. 161. 



CAETOPHYLLACEiE.— DJawMzw. Eichard. Nouv. Elemens de Bo- 

 tanique, 1846, 129.— Hartig, Th. Bot. Zeit. 1859, 109. Wood of 

 — Acantliophyllum, &c. Oliver, D, Observations on the Structure 

 of the Stem in certain species of the Natural Orders Caryophylla- 

 ceae and Plumbagineae. Linn. Trans, xxii. 289. With' 2 plates. 

 Eelating chiefly to the arrangement of the tissues in species 

 of Acantliopliylhcm. In A. spinosum, in very young internodes 

 of the stem, the pith is found to be much elongated transversely ; 

 this elongation increases until it divides the vascular zone, and 

 a belt of cambium cells encloses separately the divided por- 

 tions. In the older internodes the relative arrangement of the 

 vascular and cellular systems becomes excessively complicated 

 and no true pith is recognisable. Medullary rays are absent. 

 In the adult stems of A. spinosum spiral vessels are more or less 

 intermixed with the numerous slit-marked vessels which irre- 

 gularly traverse the parenchyma, and I have found some reason 

 to beheve that, in this and another species, in the early stages of 

 the development of the stem, prior to the dislocation of the con- 

 centric zones and tissues generally, that very narrow annular 

 belts of spiral vessels are repeated at intervals concentrically. 

 The arrangement of the woody bundles in other species of 

 Acanthophyllum is described, and attention called to the re- 

 markable abundance in the cellular tissue of the stem, of crystals 



