Filices, or ferns, structure and habitat of, i. 335 range of non-arborescent ferns, i. 335 number of species in North America, Britain, and in other places, i. 336 development of spores, i. 336, 337 roots and stems of, i. 339 leaf-stalks of, i. 340 fronds of, i. 340, 341 structure of tree-ferns, i. 341 fructification of, i. 341 sori, i. 341, 342 sporangia, i. 342, 343 foundation of the systematic arrangement of the ferns, i. 343 annulate and exannulate ferns, i. 344 Film fern, structure and habitat of, i. 362 Fire-damp of coal mines, i. 118 Fireworks, mode of the obtaining of different colours in, i. 132 Fish, phosphorescence of, i. 67 Flowering fern, i. 364 Flowers, absorption of radiant heat by the perfumes of, i. 44 weight of the perfumes, i. 45 chemical combinations forming the perfumes of, i. 97 general structure of flowering plants, i. 378 chemical nature of the colours of, i. 428, 429 Fluorescence, property of, in some solids and liquids, i. 60 Sir D. Brewster’s discovery of, i. 66 Professor Stokes’s examination of the fluorescent spectra of metals, i. 64 employed in tracing substances in impure chemical solutions, i. 67 rapid absorption accompanied by copious fluorescence, and the converse, i. 67 essential difference between fluorescence and phosphorescence, i. 67, 68 Fluorine, i. 18 Fluor spar, i. 18 crystals of, i. 18 acid obtained from, i. 18 fluorescence of, i. 60, 66 absorption of invisible rays by, i. 65 phosphorescence of, i. 66 Flustra, or sea-mat, structure of the, ii. 218 Fly fungus, i. 274 Fontinalei, structure and habitat of, i. 331 Food, miraculous descent of, i. 305 lichens as, i. 305, 308 importance of, to the animal frame, ii. 3 Foot-pound, the, of Mr. Joule, i. 26 unit of mechanical force, i. 26 Foraminifera, structure and geological importance of, ii. 27 various forms of, ii. 28 order of porcellanous foraminifera, ii. 30 order of arenaceous foraminifera, ii. 36 order of vitreous foraminifera, ii. 37 abundance of fossil foraminifera in the sedimentary strata, ii. 52 mode of obtaining casts of, ii. 53 comparison of foraminifera recent and fossil, ii. 53 the Eozoön Canadense, ii. 54 the Carpenteria a link between the foraminifera and sponges, ii. 57