Polygonacetz Rheum. 385 



in some species furnished with large sheathing bracts. Flowers 

 small, white, yellowish, or pink. Perianth composed of six 

 petaloid subequal segments. Stamens 9. Fruit triangular, 

 winged. Natives of various parts of Asia, especially the western 

 district. The name is said to be derived from RJia^ the Russian 

 name of the river Wolga, on the banks of which a species 

 of Rhubarb abounds. The species cultivated for their fleshy 

 petioles are R. Rhaponticum and R. unduldtum (fig. 206). 



1. R. Emodi. A handsome species with large slightly 

 rugose leaves having prominent red nerves. Flowers yellowish 

 white, appearing in Summer. Tartary. 



2. R. palmdtum. This species is readily distinguished by 

 its deeply divided rough foliage. Also from Tartary. 



3. R. Rlbes. This has large rounded cordate or reniform sca- 

 brous leaves and bright scarlet fruits. A native of Western Asia. 



R. nobile is a magnificent plant from the mountains of 

 Sikkim, probably not in cultivation at the present time. It is a 

 tall-growing species having large leafy coloured bracts on the 

 flower-spikes. 



The genus Rurnex, Dock, is distinguished by its perianth 

 of 6 segments, the three inner segments usually enlarging, 6 

 stamens, and trigonous fruit. R. Hydroldpathum, with oblong- 

 lanceolate leaves on long petioles, is a distinct indigenous 

 .species inhabiting ditches and ponds. 



ORDER XC.-NYCTAGINACE^l. 



Annual or perennial herbs, rarely shrubs, usually swollen at the 

 joints. Leaves opposite or alternate, and frequently unequal. 

 Flowers bisexual, capitate or solitary. Perianth inferior, 

 coloured, tubular or funnel-shaped, constricted in the middle. 

 Stamens definite, hypogynous. Fruit a 1-celled 1-seeded utricle 

 enclosed in Jhe ealarged often indurated tube of the perianth. 

 Seeds adhering to the walls of the ovary. There are about 16 

 genera and 100 species, chiefly tropical. 



1. ABRONIA. 



Herbs with opposite simple petiolate leaves and capitate 

 flowers surrounded with a finely divided involucre. Perianth 

 funnel-shaped or salver-shaped. Stamens 5. A small genus 

 of North-western American plants. The name is said to be 

 from afipos, elegant, in allusion to the involucre. 



c c 



