i. 287

Transparency in liquids and solids synonymous with discord, i. 36 causes of transparency, i. 37

Transpiration of gases, i. 110, 114

Tree ferns, structure of, i. 341

Trees, constitution of the stems of, i. 174

Tremellini, structure, habitat, and fructification of, i. 266

Trepang, used as food, ii. 184

Triceratium favus, structure and habitat of, i. 199

Triceratium genus, structure and habitat of, i. 199

Trichodesmium erythræum, structure, habitat, and reproduction of, i. 215, 216

Trichogastres, characters of the group, i. 267

Trichomanes radicans, or bristle fern, structure and habitat of, i. 361

Trichomanineæ, characters of the group, i. 345 characters and habitat of, i. 360, 361

Trilobites, structure of, ii. 203

Tripe de Roche, structure of, i. 308

Triphragmium dubens, spores of, i. 276

Tripoli stone on the Rhine, of what it consists, i. 206

Trochus granulatus, structure of, ii. 237, 238

Trochus zizyphinus, palate of, ii. 237

Truffle, structure and habitat of the, i. 292, 293 modes of tracing them, i. 293 the red, of Bath, i. 268

Trypethelium Sprengelii, pustules and sporidia of, i. 299

Tuberacei, characters and habitat of the order, i. 292

Tubicola, structure of, ii. 153 found in all seas, ii. 161

Tubipora, characters of the family of, ii. 129

Tubipora musica, structure and mode of reproduction of, ii. 130

Tubipora purpurea, habitat of, ii. 130

Tubularia, form and structure of the family, ii. 91 mode of propagation of, ii. 91

Tulip, structure and mode of reproduction of, i. 388

Tunicata, or Ascidians, characters of, ii. 222 groups of, ii. 222, _et seq._

Turbellariæ, structure of the, ii. 148

Turkey red, from what obtained, i. 124

Turpentine, oil of, takes fire in chlorine gas, i. 19

Turritopsis nutricula, larvæ of the Cunina octonaria, parasites of, ii. 100

U

Ulva, structure and reproduction of, i. 171, 225

Ulva bullosa, reproduction of, i. 227

Ulva lactuca, structure and mode of reproduction of, i. 226

Ulva latissima, structure and mode of reproduction of, i. 225-227

Ulva Linza, structure and mode of reproduction of, i. 226

Umbilicaria, structure and habitat of, i. 308

Upas-tree of Java, causes of the virulence of, i. 426 fruit of, innocuous, i. 426

Uranium, i. 4, 5 nitrate of, phosphorescence of, i. 67

Uranite, yellow, fluorescent property of, i. 66

Uredines, structure and habitat of the, i. 277

Uredo, structure and mode of reproduction of, i. 277

Uredo candida, or Cystopus candidus, structure, habitat, and mode of reproduction of, i. 278

Uredo linearis, the rust on the leaves and chaff scales of wheat, i. 281

Uromyces appendiculatus, or fungus of the common bean, i. 280

Usnea, structure of, i. 302

Usnea melaxantha, splendour of, i. 304

Usnea Taylori, splendour of, i. 304

Usneæ, brilliancy and wide diffusion of the, i. 304

Usnic acid, produced by lichens, i. 303

Uva di mare, fruit of, i. 257

V

Vacuum tubes, i. 78, _note_ electric discharges in, i. 78, 79

Valvulina, structure of, ii. 37

Vanilla, reproduction of, i. 402

Vapours, absorption of radiant heat by gases and vapours, i. 38 radiation of, equal to absorption, i. 46

Variolaria dealbata, litmus or orchil obtained from, i. 124

Vaucheria, character of the genus, i. 218, 224 structure, habitat, and modes of reproduction of, i. 218

Vaucheria marina, structure and habitat of, i. 224

Vaucheria sessilis, mode of reproduction of, i. 219

Vaucheria velutina, habitat of, i. 224

Vegetable world, microscopic structure of the, i. 167

Vegetation, i. 167 effects of light and heat on, i. 168, 169 the primordial cell, the universal framework or skeleton of the vegetable world, i. 170, 172 formation of cellular tissue, i. 171, 173 fibro-vascular bundles constituting the wood of trees, i. 173 the vascular ducts, i. 73 the pitted tissue, i. 174 the woody fibre, i. 174 sclerogen, i. 175 the laticiferous vessels, or vasa propria, i. 176, 177 seeds and spores, i. 177 cycles of existence in the vegetable world, i. 178, 186 variation of marine vegetation, horizontally and vertically with the depth, i. 258 instance of mechanical power exerted by vegetable matter, i. 269 seeds brought to Europe by the great Atlantic currents, i. 355 gradual changes of structure from the lowest to the highest cryptogamic forms, i. 375 reproduction and fructification, i. 376, 377 general structure of flowering plants, i. 378 calyx and corolla, i. 378 stamens and pollen, i. 379 pistil, ovary, and style, i. 380 fructification, i. 381 monocotyledonous, or endogenous plants, their structure, growth, and reproduction, i. 383 the earliest dawn of plant life, as shown in the colourless protoplasm of the grasses, i. 387 bulbous plants, structure and mode of reproduction of, i. 388 orchids, their structure and fructification, i. 389 dicotyledonous, or exogenous plants, i. 404-428 seeds, i. 404 stems, i. 405 stomata, i. 405, 406 bark, i. 406, 407 cambium, i. 407 wood, i. 408 roots, i. 409 leaves, i. 410 buds, spines, and hairs, i. 411 protoplasm, i. 412 chemical elements of vegetable matter, i. 413 sap and sap motion, i. 415-417 inhalation and exhalation of oxygen, i. 416, 417 latex, i. 417 milk vessels, i. 418 chemical functions, i. 419 cellulose, i. 419, 420 starch, i. 420 diastase and dextrine, i. 420, 421 sclerogen, or colouring matter of wood, i. 421 sugar, i. 421 oils, resins, and wax, i. 422, 423 albumen, fibrin, and casein, i. 423 raphides, i. 424 milk sap, i. 425 poisons, i. 425, 426 food and other purposes, i. 426 alkaloids, chemical structure of, i. 427 colouring matter of flowers, chemical nature of, i. 428, 429 water secreted by plants night and morning, i. 429 electricity developed by plants and flowers, i. 430 irritability of the tissues of plants, i. 430 light the most universal and important exciting cause in the vegetable world, i. 431

Velella spirans, structure and modes of locomotion and reproduction of,