INDEX. 283 



Himanthalia lorea, structure, fructification and habitat of, i. 256 



Holly fern, structure of, i. 347 



Holothuridae, or sea-cucumbers, structure and mode of reproduction of, 



ii. 183-186 



Hop, fungus constituting the mildew of the, i. 295 

 Honnosiphon arcticus, wide distribution of, i. 212 

 Hormotrichum, structure of the genus, i. 222 

 Hormotrichum collabens, structure and mode of reproduction of, 



i. 222 



Hyacinth, structure and mode of reproduction of the, i. 388 

 Hyalsea, structure of the, ii. 242 



Hydra fusca, structure and mode of propagation of, ii. 84, 85 

 Hydra viridis, structure and mode of propagation of, ii. 85 

 Hydra vulgaris, structure and mode of propagation of, ii. 85 

 Hydrae, structure of, ii. 81, 84 



mode of propagation of, ii. 84 



compound fresh-water Hydrae, ii. 85 



development of medusa-buds, ii. 95 



alternation of generation of hydras and medusae, ii. 96 

 Hydraulic machine, bog moss acts as a, i. 333 

 Hydridae, characters of the group, ii. 81 



Hydrobromic acid, amount of absorption of radiant heat by, i. 42 

 Hydrochloric acid, absorption of radiant heat by, i. 41, 42 

 Hydrodictyon utriculatum, structure and habitat of, i. 211 



reproduction and development of, i. 211 

 Hydrofluoric acid, i. 18 

 Hydrogen gas, i. 11 



affinity of chlorine for hydrogen, i. 19 



absorptive power of, i. 39, 41 



proportion of hydrogen to oxygen in the composition of water, i. 94 



will not combine with carbon, i. 97 



weights of the atoms of, as compared with those of oxygen, i. 99 



probable cause of its greater cooling power than that of oxygen, 

 i. 115 



one of the illuminants in coal gas, i. 118 



spectrum analysis of, i. 139, 144 



and of hydrogen, carburetted and attenuated, during and after 

 decomposition, i. 141 



carburetted, one of the illuminants in coal gas, i. 118 



marsh-gas and fire-damp, i. 118 



peroxide of, i. 9 



combination forming, i. 104 



