THE 



NATURAL ORDERS OF PLANTS. 



Class I. VASCULARES, or FLOWERING PLANTS. 



Cotyledones, Juss. Gen. p. 70. (1789.) — Embryonat>e, Richard. Anal. p. 50. (1808.) — Vas- 

 culares, Dec. Fl. Fr. 1. 68. (1815); Lindl. Synops. p. 3. (1829.)— Phanerogamous or 

 Phjenogamous Plants of authors. 



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

 ducts, and spiral vesseb. Leaves composed of parenchyma, and of veins consisting of woody 

 fibre and spiral vessels. Cuticle with stomata. Flowers consisting of floral envelopes, sta- 

 mens, and pistilla. Seeds distinctly attached to a placenta, covered with a testa, and contain- 

 ing 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 timesjiistinguish these from Cellulares, or flowerless plants, in which ducts 

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

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

 viales, which are near Algee, especially by Coniferae and Cycadese, which are 

 closely akin to Lycopodiaceae and Filices, and also by Casuarina, which must, 

 in any natural ordination, stand near Equisetaceae. 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, Monocot^le- 

 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 Exogenae or Dicotyledonous, and 

 Endogence or Monocotyledonous plants. 



Sub-Class I. EXOGENAE, or DICOTYLEDONS. 



Dicotvledonef, Juss. Gen. 70. (1789) ; Desf. Mem. Inst. 1. 478. (1796.) — Exorhizeje and Sy- 

 norhizeje, Rich. Anal. (1808.) — Dicotyledones or Exogenje, Dec. Theor. p. 209. 

 (1813.) — PhanerocotyledonejE or SeminiferjE, 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 ; in- 

 creasing 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. 

 Flowers, 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 distin- 

 guish these plants from Endogense, from which they are also known by the 

 following points : Exogenae have a distinct deposition of pith, wood, and bark ; 

 Endogenae have all these confounded : Exogenae, if trees, are conical and 

 branched (example, an Oak) ; Endogenae are cylindrical and simple-stemmed 



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