RICE. 



[ 554 ] 



ROTATION. 



II. RicciA. Archegones immersed in 

 the frond, scattered, neither emergent nor 

 exposed on the surface until burst. Peri- 

 chaete and perigone indistinguishable. Epi- 

 gone crowned by the enlarged long persistent 

 style, adherent to the sporange. Sporange 

 bursting irregularly. 



RICE. — This grain is produced by the 

 grass called Oryza sativa. The seed is 

 remarkable for the hard character of the 

 albumen, which is explained at once, when 

 we examine a section under the microscope 

 (PI. 36. figs. 12 & 13). The cells are filled 

 with very small starch -grains, which are 

 packed so closely that they assume a paren- 

 chymatous form, and present the appearance 

 of a continuous tissue (as in maize). The 

 cohesion of the starch-granules is the cause 

 of the peculiar grittiness of rice-flour. See 

 Starch. 



RIND. — This word is used to denote a 

 structure intermediate between epidermis 

 and bark ; a compound structure consisting 

 of several or many layers of cells and even 

 of distinct forms of tissue, but not presenting 

 the characteristic kinds and mode of arrange- 

 ment which occur in true Bark. 



RING-NET. See Introduction, 

 p. xxiv. We have somewhat modified this 

 ])iece of apparatus since the above was 

 written, by having the ring made of brass, 

 and the muslin fixed by means of an inner 

 ring, adapted to the outer, but incomplete 

 at one point of its circumference, and with 

 a projecting rim to prevent its passing 

 through the outer ring. The muslin is 

 retained by the spring-action of the inner 

 against the inside of the outer ring. 



RIVULARIA, Roth.— A genus of Oscil- 

 latoriacese (Confervoid Algaj), subdivided by 

 Kiitzing, and restricted to the forms in 

 which there is a distinct manubrium or elon- 

 gated cell next to the globular basal cell. As 

 thus defined, it contains only a few aquatic 

 species, the rest being transferred to Phy- 

 SACTis, EuACTis and allied genera. 



1. jR. angulosa, Roth. Frond floating, 

 globose, dirty green ; manubria oblong and 

 curved, or oblong-ovate and abbreviated ; 

 filaments torulose at the base, interruptedly 

 articulated at the apex. Eny. Bot. 968. 



2. R. Boryana, Kg. (Pl. 4. fig. 1 8). Frond 

 globose, greenish-brown ; manubria large ; 

 sheaths ventricose, colourless, with plaited 

 constrictions ; filaments moniliform or inter- 

 ruptedly articulate, flagelliform. Frond as 

 large as a cherry. /S fiaccida, smaller, fila- 

 ments flaccid, not interrupted. The follow- 



ing two are given as doubtful: R. hotryoides, 

 Carmichael, and R. plana, Harvey. 



BiBL. Kiitzing, Sp. Alg. p. 336, Tab. 

 Phyc. ii. pis. 67, 68 ; Harvey, Brit. Alg. 

 1 ed. p. 150 ; Hassall, Brit. Fr. Alg. p. 262. 

 pl. 64. 



ROCCELLA, Ach. — A genus of Parme- 

 liaceae (Gymnocarpous Lichens), growing on 

 maritime rocks, remarkable as furnishing the 

 dye called orchil or archil. R. tinctoria 

 and R. fusiformis, the British species, grow 

 only in the extreme south of England. 



BiBL. Hook. Brit. Flor. ii. pt. 1. p. 225; 

 Engl. Botany, pl. 211. 728. 



RCESTELIA, Rebent.— A genus of Cseo- 

 macei(Coniomycetous Fungi), closely related 

 to -^CIDIUM, and presenting similar sper- 

 magonia and perithecia; the chains of spores 

 of the Roesteli(B, however, present a pecu- 

 liarity, having a sterile joint, forming an 

 isthmus of variable length, between each 

 spore ; the peridium bursts irregularly, or 

 (in R. cancellata) the teeth cohere more or 

 less for a time, so as to form a kind of 

 lattice. This genus includes ^cidium cor- 

 nutum, laceratum and cancellatum of older 

 authors, growing respectively on the leaves 

 of the mountain- ash, hawthorn and pear. See 

 -^ciDiuM and Uredinei. 



BiBL. Berk. Brit. Flor. ii. pt. 2. p. 373 ; 

 Greville, Sc. Crypt. Fl. pis. 180. 209 ; De 

 Bary, Brandpilze, Berlin 1853. p. 73 ; Tu- 

 lasne, Ann. des Sc. nat. 4 ser. ii. pp. 132. 

 173 ; Fries, Summa Veg. p. 510. 



ROSALINA, D'Orb. See Foramini- 



FERA, p. 271. 



ROTALIA, Ehr. See Foraminifera, 

 p. 271. 



ROTATION.— This term is usually em- 

 ployed in botanical works to denote peculiar 

 flowing movements of the protoplasm within 

 the cavity of vegetable cells, and it is useful 

 to retain the word for all the cases of the 

 kind, in order to avoid confusion of these 

 phaenomena with the general circulation of 

 the sap. The term " circulation of the cell- 

 sap" is, however, often used instead of rota- 

 tion, and especially in reference to the cases 

 where it exhibits numerous distinct currents. 



The rotation or circulation of the proto- 

 plasm presents itself in two types, namely — 

 1. a rotatory movement of a layer of proto- 

 plasm investing the entire internal surface 

 of the cell, as in Chara, &c.j and 2. a radia- 

 ting movement of the protoplasm in slender 

 currents, from the nucleus out over the 

 remainder of the cell, with a return flow to- 

 wards the nucleus ; but as the nucleus itself 



