Plankton (Continued) 

 fresh- water, composition of, 



66-67 

 fresh-water, irregular distribution 



of, 67 

 hatching of organisms of from 



dormant condition, 87-88 

 in pond- marsh biocies, 81-82, 



82-83 

 in stream biocies, 43-44 

 kinds of, 66 

 marine: 

 as eaten by coral animals, 366 

 as not more remarkable in 

 importance than soil organisms 

 on land, 351 

 as potential food source for man, 



371 

 as whale food, 191 

 diel movements in, 358-359 

 flotation mechanisms of, 357-358 

 great variations in abundance of, 



358 

 greater abundance of in cold 



waters than in warm, 358 

 greater variety of than in fresh- 

 water, 356 

 large populations of phyto- and 

 zooplankton as not occurring in 

 same place at same time, 358 

 lower rate of productivity of in 

 cold waters than in warm, 358 

 use of nitrates and phosphates 



by as nutrient material, 354-356 

 yearly cycle in abundance of, 

 358 

 marine, composition of: 

 chordates, 357 

 coelenterata, 357 

 crustaceans, 357 

 echinoderm species, 357 

 green phytoplankton, 357 

 moUusks, 357 

 nannoplankton, 356-357 

 protozoan zooplankton, 357 

 worms, 357 

 measurement of, 39-40 

 minor importance of in fish diet, 



191-192 

 occurrence of and pH values, 66 

 productivity of and biomass, 76 

 rate of reproduction of, 204 

 release of oxygen by near water, 



63-64 

 role of in experiments to determine 

 primary production of energy, 

 203, 203-204, 204 

 role of in food-cycle of lakes, 



74 

 seasonal distribution of, 68-69 

 uncommon as source of food for 

 stream animals, 56 



Plant Ecology (see Ecology, sub- 

 divisions of) 

 Plant Reactions (see also Deserts; 

 Forests; Humidity; Lakes; 

 Light; Ponds; Precipitation; 

 Streams; Temperature; Tropical 

 Biomes; Wind): 



and ants in soil structure, 164 



and conversion of raw organic 

 matter into usable material for 

 re- absorption, 166 



and earthworms in soil structure, 

 164 



and water conditioning, 172-173 



chemical, in water, 172 



decomposition and utilization of 

 humus in soil structure, 165 



effect of dead roots on soil in, 164 



on rocks and effect on soil struc- 

 ture, 164 



physical, in water, 172 



prevailing climate as determinant 

 of, 169 



role of carbon cycle in, 167 



role of nitrogen cycle in, 166-167 

 Pleistocene Era: 



alteration of drainage patterns 

 during in northern North 

 America, 285 



climate over land bridge to 

 Siberia during, 284 



climatic conditions accompanying 

 glaciation of, 281 



cold glacial water flow during and 

 forest development, 286 



destruction of coniferous forest by 

 glaciation during, 286 



differentiation of desert vegetation 

 during, 334-335 



dispersal of isolated fauna of dur- 

 ing interglacial periods, 308 



drop in mean annual temperature 

 during, 308 



early forests of North America 

 during, 285-286 



existence of tundra during, 286 



fate of coniferous forest of North 

 America during, 286 



glaciation and wind directions in, 284 



glaciation of and Schadley pene- 

 plain, 280 



glaciation of and zonation of 

 vegetation, 313 



glaciation of as disturber of Euro- 

 pean deciduous forest biocia- 

 tion, 299 



glaciation of as enhancer of 

 differentiation of boreal and 

 western forest biociations, 308 



glacier movement from Canada 

 during, 280-281 



heavy precipitation during, 284-285 



Pleistocene Era (Continued) 

 heavy rainfall of and extension of 



grassland, 326 

 ice advance in Northern Ohio 



during, 284 

 isolation of tundra of Alaska 



refugium during, 284 

 land bridges in, 284 

 lower tree lines during than at 



present, 286 

 mammals of no longer present in 



North America, 285 

 plants and moUusks of still in 



existence, 285 

 possible southward dispersion of 



birds during due to cold climate, 



286-288 

 presence of loess in North America 



as key to absence of extensive 



forests, 286 

 refugia for coniferous forest 



survival in North America 



during, 286 

 sea level during, 284 

 segregation of animals by south- 

 ward extension of grasslands 



during, 286-288 

 substages of Wisconsin glaciation 



during, 284 

 successive thrusts of glacial ice 



in North America and Europe 



during, 284 

 survival of tundra flora in Alaska 



refugium duringglaciation of, 282 

 terrestrial biota in Europe and 



Asia during, 288 

 theory about condition of Arctic 



Ocean during, 284 

 thickness of ice during, 284 

 Pollution: 

 of lakes: 

 difficulty of controlling, 77 

 moderate degree of advantageous, 



77 

 of streams: 

 control of as basic to fish 



management, 58 

 industrial, 57 

 methods for determining degree 



of, 57 

 organic, 57 



through hydrogen sulphide, 65 

 Polymorphism (see Variations in 



Population Characteristics) 

 Pond and Marsh Management: 

 advantage of constructing artificial 



ponds, 91 

 as challenge to applied ecologists, 



92 

 awareness of relation between 



available food supply and 



population in, 91-92 



lnde> 



433 



