BOTANY. 465 



plants, of which the cotyledons or seeds are not known, and of 

 which the seminal leaves have not been observed during germi- 

 nation, are called ACOTYLEDONOUS, or not lobed ; those which 

 have but one seminal leaf or one cotyledon arQ named MONO- 

 COTYLEDOXOUS, or unilobed ; and all the other seeds contain- 

 ing an embryo of two lobes have been termed DICOTYLEDON- 

 OUS, or bilobed. 



It appears at first sight difficult to determine on viewing a 

 plant in vegetation whether it developes itself with one or two 

 cotyledons, or is destitute of any. But a little observation soon 

 overcomes this difficulty. The Acotyledoous plants have never 

 perceptible flowers nor fruits ; they are destitute of stem, roots, 

 or vessels, and their structure is cellular. All other plants are 

 provided with vessels or canals for transporting their fluids. 

 The Monocotyledonous plants have always a cylindrical stem 

 presenting outwardly circular lines or rings indicating the 

 stages of their growth. This stem is destitute of pith or me- 

 dullary substance in the centre, and has no distinct bark. 

 When cut across there are generally remarked one or many dis- 

 tinct empty fistulous canals. The leaves have almost never 

 branching ribs, but when ribs are found they are disposed longi- 

 tudinally, and in parallel lines. The Dicotyledonous plants, on 

 the contrary, are distinguished by their possessing a pith or cen- 

 tral soft substance, woody fibres, and bark. They have vessels 

 around the medullary canal, and radiated prolongations disposed 

 in such a manner that, as the plant increases in size, the inte- 

 rior vessels are obliterated and new ones developed at the cir- 

 cumference. The leaves of this division have ramified nerves, 

 commonly petiolated and jointed. Their seeds have, as the 

 name indicates, at least two cotyledons, but sometimes more ; 

 but these seminal lobes are always opposite or verticillate, and 

 the roots of the germ which they contain pierces the epidermis 

 when vegetating. 



M. de. Jussieu, to give more facility in the study of plants 

 which germinate with two cotyledons, establishes sub-classes, 

 drawn from the character of the flowers, as unisexual, her- 

 maphrodite, with or without a corolla of one or many petals ; 

 and each of these sub-classes may be divided into orders, from 

 the consideration of the insertion of the stamina. This dispo- 

 sition of the stamina, or, which comes to the same thing, of the 



VOL. II. G g 



