Lagoons formed by corals, ii. 140-143 Laminaria bulbosa, structure and fruit of, i. 248 Laminaria debilis, structure of, i. 248 Laminaria digitata, or oar-weed, structure of, i. 249 richness of the iodine obtained from, at Guernsey, i. 258 Laminaria radiata, structure, habitat, and fructification of, i. 250 Laminaria saccharina, or devil’s apron, structure and mode of reproduction of, i. 249 Laminariæ, submarine forests of, i. 248 Lanosa nivalis, the probable cause of the mildew in rye, i. 297 Lastrea, structure of the genus, i. 346 Lastrea æmula, structure of, i. 346 Lastrea filix-mas, structure of, i. 340 Lastrea rigida, scent of, i. 347 Lastrea Thelypteris or marsh fern, structure of, i. 346 Latex, structure of the, in plants, i. 417 Laughing-gas, or protoxide of nitrogen, combination forming, i. 95 Laurel, oil of, amount of radiant heat absorbed by the perfume of, i. 44 Laurencia dasyphylla, antheridia of, i. 241 Laurencia pinnatifida, or pepper dulse, structure, habitat, and mode of propagation of, i. 241 Laurencia tenuissima, antheridia of, i. 241 Laurenciaceæ, characters of, i. 240, 241 Laurentian system, ancient formation of the crystallized limestone near the base of the, ii. 54 Lavender, absorption of radiant heat by the perfume of, i. 44 Lead, its resistance to electricity, i. 90 chloride of, spectrum of, i. 146 Leathesia, structure of, i. 245 Leaves of plants, structure and functions of, i. 410 Lecanora affinis, section of, i. 300 structure and habitat of, i. 305 Lecanora esculenta, habitat of, i. 305 Lecidea, characters of the genus, i. 306 Lecidea geographica, great age of, i. 306 Lecidinei, characters of the order, i. 306 Leeches, structure of, ii. 149-151 Lemon, amount of radiant heat absorbed by the perfume of, i. 44 Lepadidæ, structure of, ii. 213, 215 Lepas anatifera, structure and mode of reproduction of, ii. 215 Lepidodendron, structure of the fossil, i. 375 Lepidostrobus ornatus, structure of, i. 375 Lepraliæ, structure of, ii. 219 Leptopteris, characters of, i. 364 Lessonia, arborescent, forests of, i. 251 Lessonia nigrescens, structure of, i. 251 rings of growth of, i. 252 Leucobryum, structure of, i. 329 Leucobryum glaucum, leaves of, i. 330 Leveillea, structure of, i. 242 Libanea crab, a parasite of the medusæ, ii. 100 Lichens, characters and habitat of, i. 298 two groups of—Gymnocarpei and Angiocarpei, i. 299 horizontal lichens, i. 299 gonidia, i. 300 asci, i. 301 thallus or frond, i. 301 dyes obtained from, i. 124, 303 brilliancy of the colours of, i. 304 Lichina, characters of the genus, i. 310 Lichinei, characters of the group, i. 310 Life, the mystery of, i. 97 instances of individual combined with a common life in the lower orders of animals, ii. 38