RHAGADOSTOMA. 



[ 656 ] 



RHIZOCLONIUM. 



RIIAGADOS'TOMA, Koib.— A genus 

 of Micro-lichens parasitic on the thallus of 

 Solorina crocea. Spores 2-4, in lanceolate 

 fugacious thecne, large, simple, becoming 2- 

 locular, colourless. (Lindsay, Qu. Mic. Jn. 

 ISm, 344.) 



RHAPIIIDOGL(E'A,Klitz.— Agenusof 

 Diatoniaceaj. 



Char. Frustules navicular, arranged in 

 radiating crowded rows in a globose gelati- 

 nous mass. INlarine. 



R. micans (PI. 19. fig. 11). Rows of frus- 

 tules irregular, obsolete ; valves linear-lan- 

 ceolate, subulate, somewhat acute. Length 

 1-140". 



Three other species. 



BiBL. Kiitzing, JJa^ill. 10 ; id. Sp. Ah/. 97. 



RAl'IIIDOMONAS, Stein.— A geiius of 

 Flagellate Infusoria. Free, green, tlagellum 

 single ; mouth anterior, with a defined pha- 

 rynx ; an anterior row of trichocvsts. Ji. 

 se7ne7i = 3Ionas s., 'Ehvh.; length 1-500"; 

 marsh-water, among decaying Sphagnum. 

 (Kent, Inf. ;191.) 



RHAPHONE'IS, Ehr.— A genus of Dia- 

 tomacefe. 



Char. Frustules single, quadrangular, na- 

 vicular ; valves without a median aperture 

 (nodule?) ; median sutural line longitudinal. 

 Marine. = Doryphora without a stalk. 



Eleven species. 



BiBL. Ehrenberg, Ber. Bcrl. Akad. 1844, 

 74 ; Kiitzing, Sp. Alq. 49. 



RUIN OPS, Hudson.— A genus of Rota- 

 toria. 



BiBL. Hudson, -4wi. Isai. Hist. January 

 1869. 



RHINOT'RTCHUM, Oorda.— A genus of 

 Mucedines (Hyphomycetous Fungi), cha- 

 racterized by more or less clavate threads 

 studded with spicules, to which the spores 

 are attached. Several species occur in this 

 country. A very beautiful rose-coloured 

 species has lately' been gathered in rabbits' 



dung. 



Ncmatozomnn, Desm., difi'ers in bearing 

 necklaces of spores. 



BiBL. Berk. Outl. 348; Cooke, Handb. 

 690. 



RHIPIDODEN'DROX, Stein.— A genus 

 of Flagellate Infusoria. Bodies ovate, con- 

 tained in elongated parallel, granular tubes, 

 forming a branched zoarv. Two species; 

 freshwater. (Kent, Inf. 285.) 



RIIIPIDOPIl'ORA*, Kiitz.— A genus of 

 Diatomaceas. 



Char. Those of Licmop)1iora, except that 

 the frustules are each furnished with a 



distinct stipes ; but as this is not always the 

 case, the character is of little or no value. 

 Marine. 



Three British species (Smith) ; twelve 

 others (Kiitzing'). 



R. 2)arachxa^{V\. 17. fig. 19). Stipes fili- 

 form, dichotomous ; frustules in front view 

 broadly wedge-shaped, somewhat acute at 

 the base. Length of frustules 1-540 to 

 4-480". 



RHIZAM'MINA, Brady.— A thread-hke 

 Foraminifer, or chitino-arenaceous branch- 

 ing tube (1-50" diam.), forming a tangled 

 weed-like tuft. R. al(/<Bformis, from 21(50 

 fathoms near Juan Fernandez. (Brady, Jn. 

 M. Soc. n. s. xix. 39.) 



RHIZIDTUM, Braun.— A genus of Uni- 

 cellular Algae, allied to Chytridium. At 

 first unicellular, then bicellular, and with 

 delicate multipartite rootlets ; cells oblong ; 

 fructiferous cells beneath the apex; zoo- 

 spores with a cilium. Parasitic in Eughnce 

 and Nitclla. 



BiBL. Braun, 3Ionatsh. 1856, 591 ; Ra- 

 benht. Ah/, iii. 284. 



RIIIZ'iNA, Fr.— A genus of Helvelloidei 

 (Ascomycetous Fungi), distinguished from 

 Peziza by the bullate hymenium, con- 

 cave beneath, and furnished with rooting 

 fibrils. 



Two species have been found in this 

 country, on sandy banks where the heath 

 has been burnt. 



BiBL. Fr. Syst. Myc. ii. 33 ; Cui-rey, Linn. 

 Tr. xxiv. 493"; Cooke, Handb. 064. 



RHIZOCLO'NIUM, Kiitz.— A genus of 

 Confervaceae (Confervoid Algae), distin- 

 guished by the decumbent habit and the 

 short, root-like appendages to the branches. 



Kiitzing includes here many of our British 

 Conferv;© : 



R. riinihirc, C. , Filaments simple, diam. 

 1-900", fine bright-green bundles 2 to 3 feet 

 long ; in streams and rivers ; common (l)ill- 

 wyn, pi. .39). 



R. fortaosjim, Dillw. Filaments simple, 

 diam. 1-800", rigid, curled and twisted, 

 forming large strata; in salt-water pools; 

 abundant (Billwyn, pi. 46). 



R. arennsmn, Carm. Filaments simple, 

 diam. 1-1000 to 1-1800"; in dirty-green 

 strata ; sandy sea-shores. 



R. ohttmanyuliim, Lyngb. (PI. 9. fig. 12). 

 Filaments branched, diam. 1-1400"; pale- 

 green, stratified; sandy sea-shores. 



R. 7-ipariu)n (Jergensii', Kiitz.). Fila- 

 ments branched, diam. 1-1400 to 1-1800", 

 Apparently not distinct from the preceding. 



