Force, i. 23 store of, eternal and unchangeable, i. 24, 25 cohesion, i. 25 in solids, i. 25 in liquids, i. 25 reciprocal attraction between solids and liquids, i. 25 unit of mechanical force, i. 26 heat generated by impetus, i. 27 unit, or mechanical equivalent of heat, i. 29 combustion a case of impetus, i. 30 energy existing in the coal fields on the globe, i. 30 magnetism and electricity, i. 30 influence of force on the aggregation of matter, i. 73 power of electricity in this respect, i. 74 relations between the force of magnetism and atoms of matter, i. 75 effect of the physical forces on molecular arrangement, i. 91 electricity, i. 91 motion, i. 91 catalysis, i. 91 force of chemical combination, i. 97, 98 relation between chemical affinity and mechanical force, i. 98 Formic acid, synthetical formation of, i. 424 Fragillaria, development of, i. 201 Fraunhofer’s lines, i. 129 Frond, or thallus, of lichens, i. 301 of ferns, i. 340, 341 Fruit, chemical combinations forming the perfumes of, i. 97 preserved, greenish and grey moulds on, i. 285 fungus on decayed, i. 290 Fucaceæ, structure and fructification of, i. 244, 250, 251 Fuci, sexual fructification of, i. 253 Fucoideæ, habitat of some, i. 256 Fucus platycarpus, male and female cells of, i. 253, 254 Fucus vesiculosus, or bladder-wrack, structure and fructification of, i. 252, 253 form of, in the Mediterranean, i. 258 Fuegians, staple food of the, i. 292 Funaria hygrometrica, structure of, i. 324, 327 Fungi, enormous numbers of, i. 260 structure of, i. 260 two principal groups of, i. 260 families of, i. 261, _et seq._ poisonous matter in all, i. 264 luminous, i. 264 stems of, i. 268 spawn of the gelatinous or creamy fungi, i. 269 universality of the lower fungi, i. 273 destruction caused by them, i. 273 parasitic fungi, i. 274 conidium, or spore-dust cell, i. 279 propagation of fungi by fragments of spawn, i. 281 extreme minuteness and profusion of fungi, i. 297 sudden and often disastrous appearance of the lower fungi, i. 297 conditions necessary to the development of fungi, i. 297 Furcellaria fastigiata, mode of reproduction of, i. 229 structure and mode of reproduction of, i. 235, 238 Fusarium tremelloides, its identity with the nettle Peziza, i. 292 G Galeolaria lutea, structure, development, and mode of reproduction of, ii. 107, 108 Garancine, from what obtained, i. 124 Gas coal. _See_ Coal gas.