MANUAL OF NATURAL HISTOEY. 439 



regions in both worlds. The roots are 

 usually purgative. (Nyctaginacece, Lindley.) 



Til. ORDER. SILENALS (Silenales). 



Flowers monodichlamydeous ; placentae free, cen- 

 tral ; carpels several, combined into a compound 

 fruit ; embryo external, curved round a little mealy 

 albumen. 



1. FAMILY. Buckwheats (Polygonacese). Herbs, 



rarely shrubs ; leaves alternate, mostly sti- 

 pulate ; stipules ochreoid ; flowers often 

 unisexual, frequently racemose ; perianth 

 divided, often coloured; aestivation, imbri- 

 cated ; stamens definite ; ovary unilocular, 

 formed of three united carpels ; styles and 

 stigmas three ; ovule orthotropal ; fruit a 

 nut, usually triangular. Distribution very 

 general. Contain much oxalic acid, also 

 nitric, malic, and tannic acids : comprise 

 Sorrel, Buckwheat, and the various species 

 of Rhubarb. 



2. FAMILY. Purslanes (Portulacacese). Shrubs or 



herbs, succulent ; leaves mostly alternate, 

 exstipulate ; flowers axillary or terminal, un- 

 symmetrical, usually ephemeral ; sepals two ; 

 petals five ; stamens variable in number ; 

 ovary formed of three united carpels, 

 1 -celled ; style single or ; stigmas 

 several ; ovules amphitropal ; fruit capsular, 

 ] -celled, dehiscent, or ] -seeded, and in- 

 dehiscent. Inhabit dry places at the Cape 



