Delesseria sanguinea, structure and habitat of, i. 239 Dematiei, structure of, i. 283 Dendritina elegans, form of, ii. 28 structure of, ii. 32 Dendritine variety of the Peneroplis, characters and habitat of, ii. 32 fossils of, ii. 33 Dennstædtia, indusium of, i. 350 Deparia prolifera, sorus and indusium of, i. 350 Desmidiaceæ, structure and development of, i. 191 _et seq._ their habitat, i. 195 Dextrine, production of in plants, i. 421 Dialysis, as a method of separating and analysing substances, i. 108 what constitutes dialysis, i. 110 Prof. Graham’s instrument for, i. 110 an extraordinary result of, i. 110 Diamagnetism, i. 75 Diamond, i. 13, 15 heat required to consume the, i. 15 crystallisation of the, i. 15 its resistance to electricity, i. 90 Dianthine, production of, i. 127 Diastase, production of, in plants, i. 420 Diatoma vulgare, structure and development of, i. 197 Diatomaceæ, or Brittleworts, found all over the globe, i. 196, 204 variety of forms of, i. 196 structure of, i, 197 development of, i. 200 social plants, i. 205 food for many aquatic animals, i. 205 fossil deposits of shells of, i. 206 enormous geological changes caused by, i. 206 Dicksonia antarctica, structure of, i. 349 Dicksonia lanata, structure of, i. 349 Dicksonia squarrosa, habitat of, i. 349 Dicksonieæ, i. 349 structure of, i. 350 Dicotyledonous, or exogenous, plants, structure and mode of reproduction of, i. 404-428 Dicranei, structure of, i. 329 Dictyopodium trilobum, structure and habitat of, ii. 20 Dictyota, structure of the genus, i. 246 Dictyota dichotoma, structure and mode of reproduction of, i. 247 Dictyoteæ, structure and mode of reproduction of, i. 246 Dictyurus purpurascens, structure of, i. 242 Difflugia, structure and minuteness of the shells of, ii. 22 their architecture, ii. 23 Difflugia pyriformis, structure, and habitat, and mode of propagation of, ii. 22, 23 Diffusibility, most substances differ in, i. 109 partial decomposition of definite chemical compounds by, i. 109 reciprocal diffusion of gases through porous plates, i. 111-113 the diffusing instrument used by Prof. Graham, i. 112 Digestion, chemical powers causing, ii. 4 Dimorphism, contrasted with isomorphism, ii. 99 Diphyidæ, structure and habitat of the, ii. 103 Diplazieæ, characters of the group, i. 352 Diplazium, structure and fructification of, i. 352 Distillation, ordinary, i. 117 destructive, i. 117 of coal, i. 117 Distomata, characters of the, ii. 146 Dracæna Draco, or dragon tree of Teneriffe, i. 387 Drummond’s light, how produced, i. 30 the continuous spectra of, i. 132 Dry rot in wood, cause of, i. 266 on various substances, i. 285 Dulses, red, i. 235 Dumontia filiformis, structure of, i. 235 D’Urvillæa, structure, fructification, and habitat of, i. 256