RHODYMENIA. 



[ 552 ] 



RHYNCHOPAGON. 



III. BOSTRYCHIA. Frond cylindrical, 

 inarticulate, dotted; the surface-cells qua- 

 drate. Tetraspores in terminal pods. 



IV. RYTIPHL^A. Frond cylindrical, in- 

 articulate, transversely striate. Tetraspores 

 in pod-like receptacles. 



V. POLYSIPHONIA. Frond cylindrical, 

 articulated wholly or in part ; the branches 

 longitudinally streaked. Tetraspores in dis- 

 torted ramuli. 



VI. DASYA. Frond cylindrical, the stem 

 inarticulate; the ramuli articulated, com- 

 posed of a single string of cells. Tetraspores 

 in pod-like receptacles (stichidid), borne by 

 the ramuli. 



RHODYMENIA, Grev. AgenusofRho- 

 dymeniaceae (Florideous Algae), containing 

 seven British species, beautiful, brightly 

 coloured sea-weeds, growing on rocks or 

 larger Algae, having a flat membranous or 

 somewhat leathery frond, ribless and vein- 

 less, of parenchymatous texture. Most are 

 not more than 2" high, but R. laciniata and 

 palmata grow to 10" and 18". The colour 

 is mostly rose- or blood-red. The coccidia 

 are formed on the lacerated margins on the 

 tips of lobes of the frond. The tetraspores 

 form cloudy spots along the margin, or 

 scattered, tetrahedrally divided. The anther- 

 idia likewise form patches on the surface of 

 the frond (observed in R. Palmetto, and 

 palmata). 



BIBL. Harvey, Brit. Mar. Alg. p. 124. 

 pi. 16 A; Thuret, Ann. des Sc. nat. 4 ser. 

 iii. p. 19. pi. 3. 



RHODYMENIACE^E. A family of 

 Florideous Algae. Purplish or blood-red 

 sea-weeds, with an expanded or filiform 

 inarticulate frond, composed of polygonal 

 cells; occasionally traversed by a fibrous 

 axis. Superficial cells minute, irregularly 

 packed, or rarely arranged in filamentous 

 series. Fructification: 1. Conceptacles (coc- 

 cidia) external or half-immersed, globose or 

 hemispherical, imperforate, containing be- 

 neath a thick envelope a mass of spores 

 affixed to a central column; 2. antheridia 

 collected in flat patches or sori; 3. tetra- 

 spores either dispersed through the whole 

 frond, or collected in indefinite cloudy 

 patches. 



Synopsis of the British Genera. 



* Frond flat, expanded, leaf-like, dichoto- 



mous or palmate. 



I. STENOGRAMME. Conceptacles linear, 

 rib-like. 



II. RHODYMENIA. Conceptacles hemi- 

 spherical, scattered. 



** Frond compressed or terete, linear or 

 filiform, much branched. 



III. SPH^ROCOCCUS. Frond linear, 

 compressed, two-edged, distichously branch- 

 ed, with an obscure midrib. 



IV. GRACILARIA. Frond filiform, com- 

 pressed or flat, irregularly branched; the 

 central cells very large. 



V. HYPNEA. Frond filiform, irregularly 

 branched, traversed by a fibro-cellular axis. 



RHOPALOMYCES, Corda. A genus of 

 Mucedines (Hyphomycetous Fungi), nearly 



Fig. 623. 



Fig. 624. 



tiun 



Rhopalomyces nigra. 

 Fig. 623. Tufts on wood. Nat. size. 

 Fig. 624. Fertile filaments. Magnified 200 diameters. 



allied to ASPERGILLUS, but having the 

 spores single (fig. 624), and not in monili- 

 form series. They are mildews growing over 

 decayed wood, matting, dung, &c. Two 

 (new) British species are described by 

 Berkeley and Broome, found growing 

 together. 



BIBL. Berk, and Broome, Ann. Nat. 

 Hist. 2 ser. vii. p. 96. pi. 5. 



RHUBARB. Garden rhubarb (Rheum 

 undulatum, and other species) affords in the 

 large edible petioles, excellent specimens of 

 SPIRAL-FIBROUS STRUCTURES, spiral, an- 

 nular and reticulate vessels and ducts ; these 

 are readily isolated by the help of a needle 

 from a fragment of cooked rhubarb placed 

 in water on a slide. The petioles and leaves 

 likewise contain bundles of acicular RA- 

 PHIDES. The roots also contain special 

 receptacles for a characteristic SECRETION. 



RHYNCHOPAGON, Werneck (Rota- 

 tori&).=Diglena with a bilobed rostrum ! 

 Two species. 



BIBL. Werneck, Ber. d. Berl. AJcad. 1841 . 

 p. 377. 



