298 INDEX. 



Orbitolites : development and varieties of, ii. 35, 36 



habitat of, ii. 36 

 Orchids, their structure, habitat, and mode of reproduction, i. 388-403 



theoretical structure of, i. 403 

 Orchil, whence obtained, i. 303 



from what obtained, i. 124 



Orchis mascula, structure and mode of reproduction of, i. 389, et seq. 

 Orchis pyramidalis, structure and mode of reproduction of, i. 393, etseg. 

 Oscillatoria littoralis, structure, and motions of, i. 213 

 Oscillatoria spiralis, motions of, i. 213 

 Oscillatorise, structure, habitat, and motions of, i. 213 



reproduction of, i. 214 



Osmunda regalis, structure and habitat of, i. 363 

 Osmundinese, characters of, i. 363 



sporangia of, i. 343 



characters of the group, i. 345 

 Ostrapods, characters of the, ii. 207 

 Otolites of Gasteropoda, ii. 236 

 Otolites of Thaumantias, ii. 93 

 Ovulata, siliceous skeleton of, ii. 60 

 Oxalic acid, former and present modes of making, i. 116 



produced by lichens, i. 303 



synthetical formation of, i. 424 

 Oxygen, i. 6-11 



effect of the combination of the atoms of oxygen and carbon in com- 

 bustion, i. 30 



absorptive power of ozonized oxygen, i. 43 



absorptive power of, i. 39, 41 



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



limit to the number of combustions of, with nitrogen, i. 95 



weight of the atoms of, in the peroxide of manganese, i. 99 



weight of the atoms of, compared with those of hydrogen, i. 99, 100 



spectrum analysis of, i. 139 



inhalation and. exhalation of, by plants, i. 416, 417 

 Oysters, iodine found in, i. 19 

 Ozone, i. 7. 



effect of the combination of ozone and oxygen in the absorption of 

 radiant heat, i. 43 



Prof. Tyndall's conjecture as to the production of ozone, i. 44 



its affinity for iodine, i. 96 



its possible effect on the solar spectrum, i. 132 



production of, i. 17 



