302 INDEX. 



Pleurocarpi, characters and habitat of the group, i. 328 

 Pleurosigma angulatum, structure of, i. 198, 199 

 Plumbago/or natural graphite, little or no porosity of, i. 112 

 Podocyrtis Schomburgi, structure and habitat of, ii. 20, 21 



fossil and existing species of, ii. 20 

 Poisons, vegetable, i. 425, 426 

 Polarization of light and heat, i. 68, 69 



relation of polarization of light and heat to crystallization, i. 70, 71 

 Pollen of flowering plants, i. 379 

 Polyatomic theory, the, i. 107 

 Polycistina, structure and habitat of the, ii. 19, 20 

 Polydes rotundis, mode of reproduction of, i. 229 

 Polygastria, a name for the Infusoria, ii. 71 



Polyides rotundus, structure and mode of propagation of, i. 237, 238 

 Polynoe, structure of, ii. 160 

 Polypary of the Alcyon zoophytes, ii. 123 

 Polypes. See Hydrozoa 

 Polypodiaceae, characters of the order, i. 344 



sporangia of, i. 343 

 Polypodineae, characters of the group, i. 344 



habitat of the, i. 345 

 Polypodium, structure and habitat of the genus, i. 345 



vulgare, fronds of, i. 340, 345 



sori of, i. 342, 345 



structure of, i. 345 



Polyporei, structure, habitat, and growth of, i. 264, 265 

 Polysiphonia, structure of the genus, i. 233 



Polysiphonia elcngata, structure and mode of propagation of, i. 234 

 Polystichum, characters of the genus, i. 347 



sorus and indusium of, i. 347 

 Polystichum aculeatum, characters of, i. 348 

 Polystichum angularum, characters of, i. 348 

 Polystichum Lonchitis, structure of, i. 347 

 Polystichum proliferum, organs of reproduction of, i. 348 

 Polystomella, characters of the genus, ii. 47 

 Polystomella crispa, form of, ii. 28 



structure and habitat of, ii. 47, 48 



cristata, form of, ii. 28 



striato-punctata, habitat of the, ii. 48 

 Polytrichei, characters of the tribe, i. 329 

 Polytrichum commune, organs of fructification of, i, 325 

 Polytrichum dendroides, structure of, i. 329 



