INCOMPLETE. 329 



bind together a rather heterogeneous series of orders. Many of them are 

 merely degraded forms of Thalamifloral or Calycifloral types. The group 

 is sometimes divided into two subdivisions, called Monochlamydeae and 

 Achlamydeae, according as there is or is not a true calyx or perianth sur- 

 rounding the stamens and pistil. A double floral envelope occurs in some 

 Euphorbiaceas, Loranthaceae, &c. Many of the plants in this group have 

 unisexual flowers grouped in cones or catkins. 



Series 1. SUPERS. 

 Ovary superior ; perianth usually distiuct. 



POLYGONACE.E. THE SORREL ORDER. 

 Coh. Chenopodiales, Benth. et Hook. 



Diagnosis. Herbs with alternate leaves, mostly furnished with 

 stipules in the form of sheaths (ocrece) above the swollen joints of 

 the stem ; the flowers mostly perfect, with a more or less persistent 

 perianth ; stamens hypogynous, or rarely perigynous ; a 1-celled 

 ovary bearing 2-3 styles or stigmas, and a single erect orthotropous 

 ovule ; fruit a triangular nut enclosing 1 erect seed, usually with 

 farinaceous perispermaudan inverted embryo. Illustrative Genera : 

 Eriogonum, L. C. Hich ; Rheum, L. ; Polygonum, L. ; Coccoloba, 

 Jacq. ; Rumew, L. 



Affinities, &c. The commoner plants of this Order may be distinguished 

 by the peculiar ocreaceous stipules (tig. 65), which, however, are wanting 

 in Erioc/onum and some other genera ; the most distinctive character- 

 istic is the solitary erect seed with its embryo having the radicle turned 

 upward ; this separates it from its near allies, the Chenopodiaceae and 

 Amarantaceae, from which also the perianth and the ocreae remove it; 

 also from the Nyctaginaceae, to which the involucrate flowers and abortive 

 stipules of Eriogonece approach. There is a further relation to Caryo- 

 phyllaceae through the Paronychiaceae. The Order is divided into tribes 

 according to the bi- or unisexual flowers, the presence or absence of an 

 involucre, the number of the parts of the flower, the presence of an 

 ocrea, &c. 



Distribution. A large Order, the members of which are universally 

 diffused ; especially abundant in temperate climates. 



Qualities and Uses. The foliage of these plants is frequently charac- 

 terized by the presence of an acid juice, depending on the presence of 

 oxalic and malic acids, or by an acrid, pungent juice ; some are strongly 

 astringent, while the roots are generally more or less powerfully purgative ; 

 the starchy perisperm of the seeds is sufficiently abundant in some species to 

 furnish a valuable substitute for corn. Among the useful acidulous kinds 

 are the garden Rhubarb, Rheum wndtdatum, R. palmatum, &c. ; the Sorrels 

 (JRumex scutatus, R. Acetosa, and R. Acetosella) are familiar plants. Rheum 

 Ribes is used for flavouring sherbet in the East ; and some other exotic 

 plants have like properties. Polygonum Hydropiper, a common native 



