RACODIUM. 



[ 547 ] 



RAPHIDES. 



placed under a cupping-glass or small bell- 

 glass, with a watch-glass containing a few 

 drops of tincture of iodine. The time 

 requu'cd for the iodizing may be about three 

 hours at 50° F., or less if the temperatm*e be 

 higher. 



The film is then covered with a solution 

 of Canada balsam in aether, saturated with 

 iodine by warming vnth a few crystals of 

 this substance, and allowing it to cool. 



Other films are removed and mounted in 

 the same manner. Should the films not 

 separate from the original liquid at the end 

 of six hom's, this must be heated mth a 

 spirit-lamp until the deposited crystals are 

 dissolved, a little spirit and a few drops more 

 tincture of iodine added, and the liquid 

 again set aside. 



If the film appear black when removed 

 on the cover, it is crossed by an adherent or 

 interposed crystal, which must be carefully 

 removed. 



These crystals are sold ready mounted, 

 and may be purchased at a very small cost. 



Dr. Herapath proposes the production of 

 the crystals of the quinine- salt as a very 

 delicate test for the presence of quinine. A 

 test-liquid is first made with 3 drachms of 

 acetic acid, 1 drachm of rectified spirit, and 

 6 drops of dilute sulphuric acid. A drop of 

 this is placed upon a slide and the alkaloid 

 added, and when it is dissolved, a very 

 minute quantity of tincture of iodine added ; 

 after a time the salt separates in little 

 rosettes. 



BiBL. Herapath, Phil. Mag. 1852. iii. 

 161, iv. 186, and 1853. vi. 171 & 346; Hai- 

 dinger, ibid. 1853. 284. 



R. 



RACODIUM, Pers. See Antennaria. 

 RADULA, Dumort. — A genus of Junger- 



Fig. 618. 



Radula complanata. 



Leafy shoot with an immature and a burst capsule. 



Magnified 5 diameters. 



manniese (Hepaticaceae), containing one 

 British species, R. complanata (fig. 618), 

 common upon the trunks of trees, every- 

 where, forming orbicular pale-green patches 

 closely appressed to the bark. 



BiBL. Hook, Brit. Jung. pi. 81, Brit. 

 Flor. ii. pt. 1. p. 120; Ekart, Syn. Jung. 

 pi. 4. fig. 31 ; Endlicher, Gen. Plant. Supp. 

 1. No. 4/2-13. 



Rx4lLFSIA, Berk. — A genus of Myrione- 

 maceae (Fucoid Algae), containing one British 

 species, R. verrucosa {R. deusta, Berk.), 

 forming dark-brown. Lichen-like patches, I 

 to 6" in diameter, on rocks between tide- 

 marks. The fronds are at first orbicular and 

 concentrically zoned ; they are composed of 

 densely-packed, vertical, simple jointed fila- 

 ments. The fruit is formed in wart-hke 

 patches, and consists of obovate oosporanges 

 attached to the bases of vertical filaments. 



BiBL. Harvey, Brit. Mar. Alg. p. 49. 

 pi. 10 D. 



RAMALINA, Ach.— A genus of Parme- 

 liaceae (Gymnocarpous Lichens), containing 

 several British species, forms of shrubby 

 habit, mostly growing upon the trunks of 

 trees, bearing orbicular, peltate apothecia, 

 nearly of the same colour as the thallus. 

 R.fraxinea, fastigiata, and farinacea are 

 common. 



BiBL. Hook. Brit. Flor. ii. pt. 1. p. 228; 

 Tulasne, Ann. des Sc. nat. 3 ser. xvii. p. 192. 

 pi. 2. figs. 13-15. 



RANA, Linn. See Frog. 



RAPHIDES. — This name was first applied 

 to the minute needle-shaped crystals occur- 

 ring in great abundance in the tissues of 

 many plants ; but it is now used in general 

 application to all the crystalline formations 

 contained in vegetable cells. The crystals 

 occur either solitary or grouped, and some- 

 times the latter are formed on a peculiar 

 stalked matrix projecting into the cavity of 

 enlarged cells, forming the organs called 

 cystolithes. 



There are few plants of the higher classes 

 which do not contain raphides ; they are 

 very abundant in the herbaceous structures 

 of the Monocotyledons generally, and espe- 

 cially those of the Araceae, Musaceae, Lilia- 

 ceae, &c. ; they also abound in the Polygo- 

 naceae, Cactaceae, Euphorbiaceae, Urticaceae, 

 &c., among the Dicotyledons. They are 

 usually found only in the interior of the ca- 

 vities of cells, but in some cases they occur 

 in the intercellular cavities, perhaps, how- 

 ever, accidentally. They may occur in al- 

 most any part, but are found most exten- 



2n2 



