2 



(example, a Palm). Besides which, the following characters, although far 

 less absolute, deserve attention ; Exogenae in germination protrude their radicle 

 at once ; while in Endogenae it is contained within the substance of the embryo, 

 through which it ultimately bursts : Exogenae have two or more cotyledons ; 

 Endogenae have but one. Exogenae approach Endogenae by Grasses and 

 Asphodeleae, winch branch like themselves, and by Smilaceae and Aroideae, 

 which have foliage resembling that of many Exogenae. The number of divi- 

 sions of their flower is hardly ever ternary, but usually some multiple of two, 

 or four, or five. In this country the trees and shrubs, and larger herbaceous 

 plants, are nearly all Exogenous ; while our native Endogenee are chiefly con- 

 fined to grasses, sedges, orchises, bulbs, and submerged water-plants. 



Exogenous plants have their seeds either enclosed in a pericarpium (Angio- 

 spermce), or naked (Gymnospermce.) . 



TRIBE I. ANGIOSPERM^E. 



These comprehend all Exogenous plants, the seeds of which are enclosed 

 within a pod, or shell, or coat proceeding from the ovarium ; in short, the 

 whole of that sub-class, with the exception of Cycadece and Coniferae. They 

 are all fecundated through the medium of a stigma and style ; while Gymno- 

 spermae, having no stigma or style, have the vivifying influence of the pollen 

 communicated directly to the seed through its foramen. The latter must not 

 be confounded with the naked-seeded plants of Linnaeus, which all belong to 

 Angiospermae, and winch are either minute fruits, or divisions of a compound 

 pistillum : they are always known by the presence of a style and stigma. 



This tribe is divided into Polypetalous, Apetalous, Achlamydeous, and JVLono- 

 pefalous plants ; of which the first three may be considered extremely artificial 

 divisions if taken separately, but forming together a tolerably natural whole ; 

 while the Monopetalous division is also, in a great measure, natural. I shall 

 therefore treat of Exogenae under two heads only. 



1. POLYPETALOUS, APETALOUS, AND ACHLAMYDEOUS 



PLANTS. 



Polypetalous plants have both a calyx and corolla ; Apetalous plants have 

 only a calyx, without a corolla ; and Achlamydeous ones have neither : but 

 these distinctions are merely artificial, and even in that point of view very 

 imperfect, — Polypetalous orders constantly containing Apetalous genera, and 

 orders with the strictest natural affinity differing in the absence or presence of 

 floral envelopes. Even Decandolle himself suggests (JWtmoire sur les Com- 

 bretacies, p. 2), that it is doubtful whether the division of Monochlamydeae 

 (which are the same as Apetalffi) is not entirely artificial. 



While, therefore, I have availed myself of these differences in framing the 

 diagnoses, and forming the artificial table, I have, in the following detailed 

 account of the orders, thrown the three divisions together, so that the mutual 

 relations of the orders may be obscured as little as possible. In using the 

 artificial tables, if an Apetalous plant cannot be referred to any order of Ape- 

 talse, its place should be sought for among Polypetala?, to some order of which 

 it will probably be found to be an exception : it is very little likely to belong to 

 Monopetalae, the Apetalous genera of which are extremely rare. There arc 

 no plants of Achlamydeoe with a calyx except some Betulinea?, the flowers of 

 which have a membranous veinless covering, of the nature of a cahyx. 



These orders pass into Monopctake through Cn prifoliaceee, among which 

 Hedera is nearly allied to Araliacea;, and through Salicariae which are very 

 near Labiatae, Meliaccae which touch upon Styraceae, and Passifloreae which 

 stand next to Cucurbitaceee. 



