‘ 
m4 AN INTRODUCTION 
CTA: PP amxy: 
Of the twenty-fecond. Clafs, Dioxrcia. 
HIS Clafs confifts of fuch Plants as 
have no Hermaphrodite Flowers, but 
bear male and female Flowers on difiind 
Plants*. The Orders of this Clafs are four- 
teen, viz. 
Oxver I. MONANDRIA, comprehend- 
ing fuch Plants as have their ma/e Flowers 
furnifhed with ove Stamen. This Order 
contains only two Genera, viz. Najas, and 
Pandanus. 
Orper II. DIANDRIA, comprehend- 
ing fuch Plants as have their male Flowers 
furnifhed with fwo Stamina. This Order 
* There are many Plants which have male and female 
Flowers on difiin Plants; but which are not admitted 
to this Clafs, becaufe this Circum{tance happens to one 
Species only, and not to the whole Genus. Inftances 
of this are met with in AZorus, Urtica, Laurus, Croton, 
Rumex, Si'ene, Carex, Rhus, Valeriana, Rhamnus,and Cu- 
cubulus. But it is obfervable, that in the Plants that 
ftand under the firft Diftin@tion. in the Order Morogynia 
of the Clafs Pentandria, which are the Ajperifolia (rcugh- 
leaved Plants) of Ray, and alfo in the Plants of the Clafies 
Didynamia, Tetradynamia, and Diadelphia, there have not 
been found any Species where the Sexes are on diftin® 
Plants: This may be accounted for from the Stru@ture 
of the Flowers in thofe Clafles, 
contains 
