RHU 



RKU 



resents a plain retort and receiver ; in 

 Fig. 2, boih are tubulated. — {Brandc.) 

 REVERBEllATUKY FURNACE 

 A Jurnacc wiili an arched roof over 

 the fire, so that the flame and heat 

 may be reflected and a liigh temper- 

 ature obtained. 



REVOl.UTE. Rolled backward. 



RHAPONTICIN and 11 H E I N. 

 Substances obtained from the roots 

 of rhubarb. 



RHEUMATISM. A nervous dis- 

 ease, sometimes attended uiih in- 

 jlammalion of the fibrous membranes 

 and sweilins of the joints. 



RHIPIPTERANS. An order of 

 insects, the Slrcpsiptcra. 



RHIZANTHS.RHIZANTPLE. A 

 small order of plants resembling fun- 

 gi, but having sexes. 



RHIZOMA. A root stock lilie that 

 of the flag. 



RHODIUM. A rare metal, of great 

 hardness, found in some of the platina 

 ores. 



RHODODENDRON. A genus of 

 handsome flowering shrubs ; they are 

 hardy, and prefer a peat soil. 



RHUBARB. Plants of the genus 

 Rheum, hardy, perennial, and large 

 herbs of the same family as the Docks. 

 The leaf stalks of several species, 

 which grow two feet and more in 

 length, are much used as a substitute 

 for gooseberries ; preserves are also 

 made of them, and even a wme of 



their juice, which is said to resemble 

 the best gooseberry wine. 



The edible kinds are Buck's new 

 scarlet, of a deep red ; the Tobolsk, 

 which is the earliest ; the Goliath and 

 Admiral, of great size ; Elfort, giant, 

 Wihnofs early red ; Myatfs Victoria, 

 of the largest sixe ; and the Austra- 

 han, which is of the flavour of apples 

 and yields stems nearly the whole 

 summer. These are varieties of the 

 Rheum rhap(i)i!icum, undidutum, and 

 Einodi {Auslralr) {Fi<r.l). They also 

 yit'lii medicinal rhubarb when the 

 roots are allowed to remain from four 

 lu seven years. But the species 

 wlikh produces the best European 

 rhubai>a is the R. palmatum (Fig. 2). 

 Fig. 2. 



The source of the Chinese drug is 

 unknown. 



Cultivation. — " The soil best suit- 

 ed to these plants is one that is light, 

 rich, deep, and moderately moist. A 

 poor, heavy, or shallow soil never 

 produces them in perlection. 



" It may be propagated by cuttings, 

 but the mode almost universally prac- 

 tised is by seed. This should he 

 sown soon after it is ripe, in Septem- 

 ber or October, for if kcjjt out of the 

 ground until the spring, it will often 

 continue dormant for twelve months ; 

 if the danger of this, however, is 

 risked, it must be inserted early in 

 February or March. The seeds are 

 best inserted in drills three feet apart, 

 and an inch deep, the plants to re- 

 main where raised ; for although 

 they will b(^ar removing, yet it al- 



660 



