620 



SYSTEMATIC BOTANY. 



Myrsinacecs, and Pluvihaginaccce. The stamens are also some- 

 times hypogynous in Ebenacece, PTlmulacccB, and Plumbaginacea, 

 and lience such plants resemble the Thalamifiorse if the petals 

 are distinct, or if united the Hypostamineoe of the Corollifiorse. 



Again, among the Epipetalse we occasionally find the ovary 

 inferior or partly so, in Ehenacecs, SfyracacecB, Myrsinacece, 

 PnrimlacecB, and always in Gesneracece, and hence such plants 

 belong to the Epigynse of the Corollifiorse, or to the Epigynse of 

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



In OlcacecB and Primulacece, apetalous species sometimes occur, 

 under which circumstances they therefore resemble the Mono- 

 chlamydese. 



Unisexual species are sometimes found in Valericmacece, Com- 

 ])osit(S, Ebenacece, Aquijoliacccs, Myrsinacece, and Planing inacea. 



Sub-class IV. Monochlamydea. 



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 Grymnospermia at 

 the end of the Monochlamydeous Orders. 



Natural Order 180. Polygonace.e. — The Buckwheat Order 

 {figs. 1002 and 1003). — Character. — Usually herbs with alter- 



Fig. 1002. Fig. 1003. 



Fig. 1002. Flower of a species of Pohioonum,- 

 of Bumex. 



-Fig. 100.3. Pistil of a species 



nate leaves and ochreate stipules {fig. 247). (The stipules are, how- 

 ever, occasionally absent, and the plants are sometimes shrubby.) 

 Flowers perfect {fig. 1002), or sometimes unisexual. Calyx^ 



* When there is but one floral envelope in Dicotyledonous 

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

 peculiarity, in which nomenclature we follow the example of 

 Lindley. By most botanists the term perianth is employed in 

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

 ledonous plants. (See page 208.) 



