SERIES III. 



PLANTS EXOGENiE, 



Dicotyledones, Jussieu. 

 Exoi-hizece, Richard. 



A LANTS composed of cellular texture, witli lymphatic, 

 spiral, and proper vessels ; and with cortical pores. Rooi 

 more or less conical, often without any pith, otherways like 

 the trunk. Trunk more or less conical, and, composed, at 

 least, of two parts growing by different modes, as may be 

 best seen in the arborescent species, in which we find P. a 

 central pith enclosed in a medullary canal, emitting on all 

 sides radiating medullary productions ; 2°. annual layers, 

 more or less woody, disposed concentrically round the pith, 

 the outer layers being the youngest and the least hard ; 

 3". cortical layers, distinct from the wood, but scarcely dis- 

 tinguishable from one another, and differing from the last 

 in the mode of growth, the inner ones being the youngest, 

 and the external being the oldest. Leaves opposite or ver- 

 ticillate, sometimes becoming alternate by the growth of 

 the stem, disposed more or less spirally on the stem, often 

 articulated on the stem, or truly compound ; always fur- 

 nished with ribs that anastomose with one another. Flowers 

 always distinct, usually furnished with a double perigonium, 

 parts usually five in number, or divided into five segments. 

 Stamens rarely 3, 6, or 9, or any multiple of 3. Corculum 

 rnost commonly with 2 cotyledons. Cotyledons 2, placed 

 opposite, never alternate ; very rarely many, verticillate ; 

 and, in leafless plants, none. 



This series con.tains full two thirds of the whole number 

 of natural families; but the arrangement of these families 

 among themselves has not yet been determined, and there- 

 fore the families of this series are arranged by ]3e Candolle, 

 for the present, into four artificial subseries resting upon 

 the differences observable in their petals and staniens, until 

 a natural arrangement by their affinities shall be discovered. 

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