THE 



NATURAL ORDERS OF PLANTS. 



Class I. VASCULARES, on FLOWERING PLANTS. 



C'otvledone.t:,>/?/«s. Gen. p. 70.(1789.) — Embrvonat^e, lUcliard. Anal.p.50. (1808.) 

 — Vasculares, Dec. Fl. Fr. 1. OU (1815); Lindl. Synops.j?. 3. (1829.) — Pha- 

 nerogamous or PHyENOGAMOUS PLANTS of authors. 



Essential Character. — Substance of the plant composed of cellular tissue, woody- 

 fibre, ducts, and spiral vessels. Leaves composed of parenchyma, and of veins consisting 

 of woody fibre and spiral vessels. Cuticle with stomata. Floivers consisting of fioral en- 

 velopes, stamens, and pistilla. Seeds distinctly attached to a placenta, covered with a testa, 

 and containing an embryo with one or more cotyledons ; germinating at two fixed points, 

 the plumula and radicle. 



The presence of flowers, of spiral vessels, and of cuticular stomata, will at 

 all times distinguish these from Cellulares, or flowerless plants, in which ducts 

 sometimes exist, but which never have spiral vessels. Vasculares approach 

 Cellulares by Podostemeoe, some of which resemble Azolla in habit, by Flu- 

 viales, which are near Algge, especially by Coniferee and Cycadese, which are 

 closely akin to Lycopodiacese and Fihces, and also by Casuarina, which must, 

 in any natural ordination, stand near Equisetaceee. Besides the more obvious 

 points of difference just adverted to, Vasculares differ from Cellulares in their 

 embryo ; not, however, in the number of the cotyledons, as is generally sup- 

 posed in consequence of the common names of Dicotyledones, Monocotyle- 

 dones, and Acotyledones,but in the germination of the seeds of the two former 

 always taking place from two fixed points, and in the latter from no fixed point. 



Vasculares are divided into the sub-classes Exogence or Dicotyledonous, 

 and EndogencB or Monocotyledonous plants. 



Sub-Class \. EXOGEN^, or DICOTYLEDONS. 



Dicotyledones, Juss. Gen. 70.(1789); Desf. Mem. Inst. 1. 478. (1796.)— Exoh- 

 HizE^ and Synorhize^, Rich. Anal. (1808.) — DicoTYLEDONEyE or Exo- 

 GEN.E, Dec. Theor. p. 209. (1813.) — PhanerocotyledonEjE or Seminifer.e, 

 Agardh. Aph. 74. (1821.) 



Essential Character. — Trunk more or less conical, consisting of three parts, one 

 within the other ; viz. bark, wood, and pith, of which the wood is enclosed within the two 

 others ; increasing by an annual deposit of new wood and cortical matter between the 

 wood and bark. Leaves always articulated with the stem, often opposite, their veins 

 branching and reticulated. Flou-ers, if with a distinct calyx, often having a quinary 

 division. Embryo with two or more opposite cotyledons, which often become green and 

 leaf-like after germination ; radicle naked, i.e. elongating into a root without penetrating 

 any external case. 



Their reticulated leaves, distinctly articulated with the stem, usually dis- 

 tinguish these plants from Endogense, from which they are also known by 

 the following points : Exogenee have a distinct deposition of pith, wood, and 

 (bark ; Endogense have all these confounded : Exogenae, if trees, are conical 

 and branched (example, an Oak) ; Endogenge are cylindrical and siniple- 



B 



