Ramalina calicaris, gluten of, i. 303 Ramalina polymorphum, dyes obtained from, i. 303 Ramalina scopulorum, dyes of, i. 303 Raphides, structure and formation of, i. 424, 425 Red Sea, foraminifera in the, ii. 51 Reed, Cordyceps on the ergot of the, i. 293 Reed, Italian, vegetable tissues represented in, i. 175, 176 Reef-building corals, ii. 138-142 Reefs, barrier, formation of, ii. 143 Resins, formation of, i. 422 Respiration, chemical powers causing, ii. 4 Respiration of the muscles, ii. 8 Reticularia, characters of the order, ii. 24 Reticularia maxima of cucumber beds, i. 269 Rhabdonia Coulteri, mode of propagation of, i. 236 Rhamnus cathartica, M. Charwin’s discovery of a green dye obtained from the, i. 124 Rhizocrinus Lofotensis, structure of, ii. 175 Rhizopoda, structure of the, ii. 13 simple Rhizopods, forms of, ii. 22 Rhizoselenia, enormous masses of, in the Indian Ocean, i. 205 Rhizospermæ. _See_ Marsileaceæ Rhizostoma, or many-mouthed medusæ, structure and mode of reproduction of, ii. 97, 98 food of, ii. 98 Rhodomelaceæ, structure &c. of, i. 241 Rhodospermeæ, characters of the, i. 180 structure and mode of reproduction of, i. 227, _et seq._ causes which affect the form and limits of, i. 243 Rhodymenia palmata, structure and mode of reproduction of, i. 236 Rhodymeniaceæ, structure of, i. 236 Ricciaceæ, or Crystalworts, characters of the order, i. 316 Richmond, in Virginia, siliceous deposit upon which it stands, i. 206 Riella, characters of the genus, i. 316, 317 Rivularia, structure of the genus, i. 213, 215 Rivularia nitida, structure and motions of, i. 213, 215 Rocella fuciformis, dye and orchil obtained from, i. 303 Rocella tinctoria and fusiformis, blue and purple dyes obtained from, i. 124 Rock-crystal, formation of, i. 17 Rock-salt, chlorine obtained from, i. 18 permeable to radiant heat but radiates badly, i. 37 Roots, downward tendency of, i. 382 structure and functions of, i. 409 Rosalina ornata, structure of, ii. 41 Rosaniline, or roseine, the base of aniline, i. 123 production of, i. 123 Rosaniline, chemical composition of, i. 128 Rosemary, amount of radiant heat absorbed by the perfume of, i. 44 Roses, otto of, amount of radiant heat absorbed by the perfume of, i. 44 Rotalia, structure of, ii. 38 Rotalia Beccarii, habitat and structure of, ii. 42 Rotaline group of foraminifera, ii. 44 Rotifer, common, structure of the, ii. 167 Rotifera, characters of the, ii. 162 mode of reproduction of the, ii. 162 Rubia tinctorum, madder obtained from the roots of, i. 124 Rubidium, i. 3, 4 atomic weight of, compared with that of hydrogen, i. 100 one of an isomeric triad with cæsium and potassium, i. 105 M. Bunsen’s discovery of the metal by spectrum analysis, i. 134, 135 mode of distinguishing it from potassium, i. 135 properties of, i. 136 where found, i. 136 Ruby, i. 4