Siberian conifers, 346, 348 



— Dwarf-pine, see Piniis pitmila 



— Fir, see Abies sibirica 



— Larch, see Larix sibirica s.l. 



— Spruce, see Picea obovata 



— Stone-pine, see Piniis sibirica 

 Sierra Redwood, see Sequoiadendrofi 



giganteum 

 Sigillaria (Sigillarias), 137, 148 

 Significance and distribution of plant 

 diseases, 250-3 



of weeds, 248-50, 253 



Silene (Campion), 219 



S. acaulis agg. (Moss Campion), 108, 



284, 285 

 5*. linicola, 219 

 Silica, 56, 298, 476, 497 



— secreted by Diatoms, 34, 497 

 Siliceous deposits, 34, 497, 547 

 Silicoflagellates, 517 

 Silkweed, see Asclepias 

 Silting, 293, 325, 369, 456, 476, 505, 



524. 555 

 — , Char a and, 503 



Silurian period, 129, 133, 137, 145, 146 

 Similarity of floras in N. America and 



E. Asia, 157, 161, 167 



— of organisms in Australia and S. 



America, 170 

 Sinkholes (swallow-holes), 546 

 Sinnott, E. W., 579 

 Sisal, see Agave 



Sisymbrium sophia (Flixweed), 125 

 Sizing of paper, 265, 269, 272, 273 

 Skunk-cabbage, see Symplocarpus foeti- 



dus 

 Slash Pine, see Pimis caribaea 

 Slerozem, 300 



Slime-moulds, see M>Tcomycetes 

 Slippery Elm, 264 



Slope, ecological significance of, 296, 375 

 • — , infialittoral, 492, 493 

 Slug, 117, 306 

 Smilax (Catbriar), 262 

 Smith, A. L., 74 

 — , G. M., 74, 506, 540 

 — , W. Wright, xvii 

 Smoking materials, 266-7 

 Smother crops, weeds and, 280 

 Smuts {see also Fungi), 43, 251, 280 

 Snail, 117, 305, 306 

 Snipe, 114 

 Snow {see also Precipitation), 11, 93, 



290, 345> 350, 381, 392, 479, 506 

 — , Algae on, 333, 476, 489-91 

 — , Bacteria on, 419, 491 



— Bunting, 116 

 — , coloured, 490 



drift, 292, 315, 393, 394. 395, 402-5 



flea, 490 



melt, dispersal by, 107, 108 



INDEX 629 



Snow-patches (late-snow), vegetation 

 and, 393, 394, 398, 402-3, 404,405, 

 411 



Soap, 265, 266, 275 



- — substitutes, lather-forming, 266 



Soapbark tree, 266 



Soapberry, 266 



Soaproot, 266 



Soapwort, 266 



Socies, 334 



Society, layer (stratal), 334 



— , plant, 334, 360, 383 



Sodium chloride, 368, 508 



Soft bottoms. Algae of, 492, 528, 529-33 



— water, 373, 478 

 Softwoods, 246, 268 

 Soil, accumulation of, 327, 371, 372 

 — , acid (acidic), 303, 358 

 — , aeration of, 302, 305, 501 



— Algae, 29, 32, 34, 304, 333 



— atmosphere, 302 



— Bacteria, 26, 303, 305, 333 

 — , calcareous, 79, 302, 355, 356, 373, 

 — , calcium carbonate in, 79 [397, 443 



— classification, 297, 298 

 — , climatic types of, 297-8, 300 



— colloids, 298 



— communities, 303, 316, 333 



— conditions and plant growth, 79 



— constituents, 298-304 

 — , crumb-structure of, 298 

 — , cultivation and stratification of, 297 

 — , decomposition in, 302-3, 305 

 — , desert, 365, 366, 368, 449-52, 453 



— fractions, 298 



— Fungi, 45, 303, 305, 333 



— groups, world map of, 300 



— horizons, 297, 299 



— map, 300, 568 

 — , maturation of, 298, 390 

 — , mechanical analysis of, 298 

 — , — constitution of, 298, 301 



— microcosm, 297, 304 

 — , mineral constituents of, 298 



— moisture, 279, 301-2, 381 

 — , nature of, 297 



— organisms, 297, 302, 303, 304, 333 

 — , patterned, 385 

 — , permanently frozen, 381, 384 



— polygons, 370, 381, 385, 387, 395, 

 — , prairie, 298, 299 [39^ 



— profile, 297, 299 



— reaction {see also pH), 302, 303, 373, 



salinity, persistent, 370 

 — , salts in, 301-2, 36S 

 — , sandy, 301 

 — , stratification in, 297, 299 



— temperature, 288, 304 



— texture, 279, 297 

 — , toxins in, 304 



— water, 298, 301-2, 321 



[374 



