INDEX. 303 



Polyzoa, or Bryozoa, characters of, ii. 218 



Polyzonia cuneifolia, structure of, i. 242, 243 



Porites, or reef-building corals, ii. 140 



Porphyra laciniata, structure and habitat of, i. 227 



Porphyra vulgaris, structure, habitat, and mode of reproduction of, i. 227 



Porpita, characters of the genus, ii. 117 



glandifera, structure, habitat, and mode of reproduction of, ii. 117 



118 

 Potash, caustic, effect of the heating of, by an electric discharge, i. 84 



its effect on electricity in a vacuum tube, i. 86 



cyanite of, combination forming, i. 106 



nitrate of, its opacity to the invisible rays, i. 65 



oxalate of, formation of, i. 117 



violet coloured light obtained by the combustion of, i. 133 



in the land plants, i. 414 

 Potassium, i. 3 



affinity for oxygen, i. 96 

 atomic weight of, compared with that of hydrogen, i. 100 



one of an isomeric triad with caesium and rubidium, i. 105 



iodide of, whence obtained, i. 19 

 Potato, fungi causing the murrain in the, i. 284, 285 



mode in which the injury is done, i. 284 



poisonous nature of the leaves and berries of the, i. 426, 427 

 Poulpe, structure of the, ii. 245 



Praya diphys, structure and mode of reproduction of, ii. 103-106 

 Propagation of diatoms by bisection, by conjugation, and by gonidia, 



i. 200 



Protein produced by plants, i. 419 

 Protococcus pluvialis, structure and development of, i. 184 



cycles of reproduction, i. 186 



Protococcus viridis, abundance of, found in dust from Egypt, ii. 65 

 Protophytes, structure and development of, i. 182 

 Protoplasm of plants, structure and function of, i. 412, 413 

 Protozoa, structure of the, ii. 13 

 Pteridae, characters of the group, i. 357 

 Pteris, characters of the genus, i. 357 

 Pteris aquilina, stems of, i. 339 



or bracken, structure, mode of reproduction, and habitat of, i. 



357, 358 



Pteris esculenta of New Zealand, i. 358 

 Pteris serrulata, development of spores of, i. 337 



antheridium and spermatozoids of, i. 338 



