pollen mother cell . A special case of spore mother cell.
GeoWord of the Day
The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.
coal classification . (a) The analysis or grouping of coals according to a particular property, such as degree of metamorphism (rank), constituent plant materials (type), or degree of impurity (grade). (b) The analysis or grouping of coals according to the percentage of volatile matter, caking properties, and coking properties.
sedimentation balance . An apparatus used to measure the settling rate of small particles dispersed in a liquid.
fragment (frag'-ment). (a) A rock or mineral particle larger than a grain. (b) A piece of rock that has been detached or broken from a preexisting mass; e.g. a clast produced by volcanic, dynamic, or weathering processes.
stress . (a) In a solid, the force per unit area, acting on any surface within it, and variously expressed as pounds or tons per square inch, or dynes or kilograms per square centimenter; also, by extension, the external pressure which creates the internal force. The stress at any point is mathematically defined by nine values: three to specify the normal components and six to specify the shear components, relative to three mutually perpendicular reference axes. Cf: strain. See also: normal stress; shear stress. (b) A commonly used short form for differential stress.
conical fold (con'-i-cal). A fold model that can be described geometrically by the rotation of a line about one of its ends, which is fixed. Cf: cylindrical fold.
biochronozone (bi-o-chron'-o-zone). A chronozone based on a biostratigraphic unit, e.g. Cardioceras cordatum biochronozone (NACSN, 1983, Art. 75). Cf: lithochronozone; polarity chronozone.
suberinite (su'-ber-in-ite''). (a) A variety of provitrinite characteristic of suberain and consisting of corky tissue. (b) A maceral of brown coal and lignite derived from the suberin layer in corkified cell walls of some Mesozoic and younger plants. (c) A maceral of the liptinite group. Cf: periblinite; xylinite; telinite.
stalagmite [speleo] (sta-lag'-mite). A conical or cylindrical speleothem that is developed upward from the floor of a cave by the action of dripping water. It is usually composed of calcite but may be formed of other minerals. Cf: stalactite [speleo]. Etymol: Greek, "drop (something that has dripped down)". The term was first used by Worm in 1642.
lindoite (lin'-do-ite). A light-colored hypabyssal rock characterized by bostonitic texture and similar in composition to sölvsbergite, but being rich in quartz and poor in dark-colored minerals; the extrusive equivalent of an alkalic granite. The name, given by Brögger in 1894, is for the island of Lindö, Oslo district, Norway. Obsolete.
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