312 * OBTCilNAL ARTICLES. 



diiferential characters presented by tlie species have but a secon- 

 dary importance. 

 Cactaceae. De Caudolle, A. P. Eevue de la Famille, in Mem. du Mu- 

 seum, 1828, x\di. Latige, p. 5. — Scbleiden, Wiegmann's Arch. 1839, 

 pt. 3, A. N. H. iv. 245. In Melocactus, Echinocactus, Mammillaria, 

 the wood consists akoost entirely of short, broad, thin-walled cells, 

 obtusely conical at ends, with very thick annular or spiral cells. — 

 Also in Beitrage zur Anatomic der Cacteen ; with 10 plates. 

 The vascidar bundles occur under three modifications. 1. Pos- 

 sessing liber, and corresponding to the usual structure of the vas- 

 cular bundle in Dicotyledons, excepting that in the later-formed 

 wood-layers spiral vessels are found. 2. Bundles in which the 

 liber is replaced by gum-canals. 3. Yascvdar bundles with cells 

 having flattened, projecting rings in the interior and spiral vessels. 

 These cells are wanting in Pereskia, Rhipsalis, Cereus, and flat- 

 stemmed Opuntias ; they form the main part of the wood in 

 Echino- and JSIelocactus. In Mammillaria , with a few spirals in 

 the medidlary sheath, they form the entire wood-mass. Ann nal 

 zones do not occur. Eings of wood formation answering to con- 

 siderable periods of time are found : their cause is uncertain. A 

 detailed account is given of the various tissues of the stem. — 

 EcTiinocactus, Melocactus. Brongniart, A. Obs. sur la structiire 

 du SigiUaria, Sfc. Arch, du Museum (1839), i. 442. Tab. xxxv. 

 Independent vascular bundles are found scattered in the pith of 

 some species. — Meyen, F. J. E. Neues System d. Pflanz. 

 Physiol, (fig. tab. i. and iii.) — Harting, P. Bijdrage tot de Ana- 

 tomic der Cacteen., v. der Hoeven imd Vriese, Tydschrift, 1842, 

 181, with 2 plates — Graudichaud, Guillemin's Archives, ii. 502. 

 pi. 19.- Schleiden, Principles Bot. 255.— A. Trecul, Extrait d'un 

 Memoire inedit sur les formations spirales, annidaires et reticu- 

 lees, &c., Bull. Soc. Bot. i. 67. Eeferring especially to the 

 structure and development of the spiral fibres in the wood cells.— 

 Trecul, A. Compt. Eend. 1854, t. 38, 114^5.— Cactus. Meyen, 

 E. J. E. Phytotomie, 1830. tab. x. 1. 4.— Corda. Ban des Pflan- 

 zenstammes, in AVeitenweber's Beitrage z. Nat.und Heilwiss. Prag, 

 1836,— C. cliilcnsis. Meyen, E. J. E. Anat. imd Phys. d. Gewachse, 

 1836, tab. viii. 24-5. (other Cactaceae) tab. ix. — Cactus. Meyen, 

 E. J. E. Neues System Pflz.-Physiologie, 1837, tab. i. 1, 5, 8- 

 10. — Cereus. Tur])in, P. J. E. Analyse Microscopique du tissu 

 cellulaire de la moelle et de I'ecorce, &c. Ann. Sc. Nat. 1830, 

 20-26— Link, H. E. Anatomia plantarum, 1843. tab. iii. 1-6, 

 EpipJnjllum, Opunfia, Cereus. — Link, H. E. Icones Selecta, 1840, 

 Ease. ii. iii. — Iihip6alis, ^'C. tab. iv. 5-11. — Ilelocacttis. Miquel, 

 E. A. W. Monographia generis Melocacti, Nova Acta Ac. 

 Caes L. C. 1841. xviii. Suppl. i. Truncics, p. 115. — also 

 Anatomische Bemerkungen iiber den Ban der Melocacten. Lin- 

 naea. 1842, 465. Ann. Sc. Nat. ii. Ser. xix. 164. Supplying a 

 lacune in Schleiden's observations. A minute account of the in- 



