620 SYSTEMATIC BOTANY. 



Again, among the Epipetalce we occasionally find the ovary 

 inferior or partly so, in Ebenacece, Sti/racacece, Myrsinaceat, 

 Primulacece, and in Gesneracece always, and hence such plants 

 belong to the Epigynoe of the Corollifloras, or to the Epigynae of 

 the Calyciflorse, according as their petals are united or distinct. 



In OleacecB and Primulacece, apetalous species occur, and 

 therefore resemble the Monochlamydese. 



Unisexual species are {oxm&mVakrianacecB, Composita, Ebe- 

 nacecB, AquifoliacecE, Myrsinacece, and Plantayinaceoe. 



Sub-class IV. — MonoclilamydecB. 



This sub-class is commonly divided by botanists into two 

 sub-divisions, called respectively, Angiospermia and Gymno- 

 spermia, but the plants of the latter group present such striking 

 differences in their structural and physiological characters from 

 those of other Dicotyledons, that we have placed them in a 

 division by themselves under the name of the Gymnospermia 

 at the end of the Monochlamydeous Orders. 



Natural Order 180. Polygonace^. — The Buckwheat Order 

 (^figs. 1001, 1002). — Usually herbs with alternate leaves 

 and ochreate stipules (^fig. 254). (The stipules are, however, 



Fig. 1001. Fig. 1002. 



Fig. 1001. Flower of a species of I'ohjaonum Fig. 1002. Pistil of a species 



of Jiuinex. 



occasionally absent, and the plants are sometimes shrubby.) 

 Flowers perfect (Jig. 1001), or sometimes unisexual. Calyx* 

 free (Jig. 1001), more or less persistent, imbricated Stamens 

 (Jig. 1001), hypogynous or perigynous ; anthers dehiscing lon- 



• When there is but one floral envelope in Dicotyledonous 

 plants, wc call that the calyx, whatever be its colour or other 

 peculiarity, in which nomenclature we follow the example of 

 Lindlcy. ]5y most botanists the term perianth is employed in 

 such cases, but wc use that name only in speaking of Monocoty- 

 ledonous plants. 



