Verrucariei, structure of, i. 310 Verrucaria muralis, structure and habitat of, i. 310 Verrucaria variolosa, structure and development of, i. 299, 300 Vibrissea, motions of the sporidia in, i. 292 Vibrios found in dust from Egypt, ii. 65 agents in the decomposition of organic matter, ii. 66, 67 difference between vibrios and mycoderms, ii. 66 extreme tenacity of life of the vibrios, ii. 67 Vine, fungus constituting the mildew of the, i. 295, 297 Vinegar plant, fungus producing the, i. 288 Virgularia juncea, ii. 129 Virgularia mirabilis, mode of reproduction of, ii. 129 Virgulariæ, structure and mode of reproduction of the, ii. 129 Vis viva, or impetus, i. 26, 27 heat generated by, i. 27 combustion, a case of, i. 30 Vittarieæ, characters of the group, i. 356 Volatility of a compound, law of, i. 22 Voltaic battery, i. 31 Voltaic electricity. _See_ Electricity Volvocineæ, structure and reproduction of, i. 187, 189 Volvox globator, structure and development of, i. 189 Vorticella nebulifera, diversity of their reproductive powers, ii. 75, 76 Vorticellæ, structure of the, ii. 76 food of, and mode of taking it, ii. 76, 77 mode of reproduction of, ii. 77 Vulpinic acid, whence obtained, i. 303 W Walking fern, structure and mode of reproduction of, i. 352 Walnut, cause of blistered leaves of the, i. 291 Wasp, a West Indian, killed by fungi, i. 293, 294 Water almost impervious to heat, i. 36 proportions of oxygen and hydrogen in, i. 94 combination and decomposition of, i. 94 force of the chemical combination requisite to form a gallon of, from the combustion of the two gases, i. 97, 98 force required to freeze water, i. 98 amount of voltaic electricity required to separate a given quantity of water into hydrogen and oxygen, i. 101 the most common radicle in the inorganic and organic world, i. 107 the water of crystallization, and the effect of heat upon it, i. 108 production of aqueous solutions of organic and inorganic matter, i. 111 water secreted night and morning by plants, i. 429 Water-flea, arborescent, structure of the, ii. 208 Waterproofing, India rubber prepared for, i. 120 Wax, vegetable, formation of, i. 422, 423 functions of, i. 423 Wheat, probable causes of the rust and smut of, i. 281 Cordyceps on the ergot of, i. 293 Whelks, tongues of, ii. 239, 240 Wood-louse, or slater, structure of, ii. 202 Wood of trees, fibro-vascular bundles constituting the wood of, i. 173, 174 structure of, i. 408 Woodsia, structure of, i. 349 Woodsia ilvensis, structure and fructification of, i. 350 Woodsieæ, or Peranemeæ, characters of the group, i. 350 Worms, or annulosa, characters of, ii. 144 Wormskioldia sanguinea, structure and habitat of, i. 239, 240 Wormwood, absorption of radiant heat by the perfume of, i. 44 Wrangelia penicillata, spores of, i. 237