916 



Yearboo^ of Agriculture 1949 



teristics as to indicate a high relationship 

 as well as common origin and descent. It 

 is the unit of plant and animal classification. 



STEM The main axis, trunk, or body of 

 a tree or other plant. 



STOMATA (plural) ; STOMA (singular) 

 Minute openings, chiefly on the surface of 

 the leaves of plants, through which water 

 is evaporated and through which gaseous 

 exchange takes place. Stomata are physiolog- 

 ically regulated by the plant. 



STRATIFICATION The operation or meth- 

 od of burying seeds to keep them fresh and 

 to soften their coverings, or to expose them 

 without injury to cold temperatures that 

 they may be more readily germinated, that 

 is, for storage or to overcome dormancy. 



STUM PAGE The value of timber as it 

 stands uncut in the woods; in a general 

 sense, the standing timber itself. 



SUCCESSION The process of replace- 

 ment of one plant community by another 

 until the climax is reached. Each com- 

 munity in turn changes the temperature, 

 moisture, and other factors of the environ- 

 ment; these new conditions hinder the com- 

 munity that brought them about and favor 

 a new one, which becomes the next step in 

 the succession. 



THINNING A cutting made in an im- 

 mature stand for the purpose of increasing 

 the rate of growth and improving the form 

 (or quality) of the trees that remain and in- 

 creasing the total production of the stand. 



TOLERANCE The ability of a tree to with- 

 stand extreme conditions of shade, disease, 

 or other hazards. 



TRANSPIRATION The process by which 

 trees or other plants remove water from 

 the soil and pass it through their roots, up- 

 ward through the trunks and branches, and 

 then out through the leaves into the air. 

 Transpiration is a physiological process reg* 

 ulated by a living organism; evaporation is 

 a physical process such as evaporation of 

 water from the surface of a lake. 



UNDERSTORY That portion of the trees 

 in a forest that is below the level of the 

 main canopy; also, the trees forming such 

 a layer. 



VAN The small store in a logging camp 

 in which clothing, tobacco, and medicine 

 are kept to supply the crew. A portable van 

 is also used, particularly on long river drives. 



VASCULAR Of or pertaining to a vessel 

 or vessels for the conveyance of a fluid, 

 especially (in animals) a nutritive fluid, as 

 blood or lymph, or (in plants) the sap; 

 designating, or pertaining to, the entire 

 system of vessels having this function. 



VEGETATIVE Applied to propagation of 

 plants by rooting cuttings or slips, budding, 

 or grafting. This type of propagation leads 

 to the formation of a clone if all the cut- 

 tings, buds, or cions are taken from the 

 same seedling, and is to be distinguished 

 from sexual or seed propagation. For this 

 reason, the term asexual propagation is 

 sometimes used. 



VENEER A thin sheet of wood produced 

 by rotating a log or bolt against a knife in 

 a lathe or by sawing or slicing. 



VIRGIN (of forests) A mature or over- 

 mature forest growth essentially unin- 

 fluenced by human activity. Virgin forests 

 are also referred to as "old-growth" forests, 

 as contrasted to newer or "second-growth" 

 forests. In Douglas-fir, trees more than 200 

 years old are generally considered to be 

 "old growth." 



WATER TABLE When water occupies a 

 zone of saturation beneath the ground, the 

 upper edge of this zone is called the water 

 table. If the table is tilted, the water moves 

 toward the low side in an effort to make 

 the surface level. When the water table 

 intersects the land surface, as in a valley 

 bottom, the ground water is drained by 

 means of surface stream. See GROUND 

 WATER. 



WIDOW MAKER A broken limb hanging 

 loose in the top of a tree, or a chunk or 

 limb knocked loose by a falling tree. 



WINDFALL A tree knocked down by the 

 wind. An area of such trees. Synonym: 

 Blow-down. 



WOODPECKER A poor chopper. Syno- 

 nym: Beaver. 



WORKING CIRCLE A unit of forest land 

 that is handled in accordance with a spe- 

 cific plan of management for the timber 

 resources of that area. 



WOLF TREE A forest tree whose size and 

 position cause it to prevent the growth of 

 many small trees around it by usurping 

 their space, light, and nourishment. 



WEED TREE A tree that has little or no 

 commercial value. 



