Glossary - Tropical Forest Biomes - page 232

Ratite. A flightless bird lacking a broad sternum for the attachment of wing muscles.
Large tropical grassland birds well adapted to running, ratites include ostriches,
emus, cassowaries, and rheas.
Reed. A large hollow-stemmed grass of genera such as Arundo and Phragmites , possess-
ing plume-like inflorescences.
Rhizome. Underground stems from which new plantlets or tillers arise, leading to the
sod-forming habit of some grasses.
Ruminant. An artiodactyl that possesses a four-chambered stomach in which grasses
ferment and that chews its cud.
Sedge. A grass-like flowering plant in the family Cypercaceae. Members of the genus
Carex usually prefer damper conditions than grasses.
Semiarid. Referring to climatic conditions in which there is too little precipitation to
support forests, but no so little that deserts prevail. In the mid-latitudes, semiarid
regions usually receive between 10 and 20 in of precipitation a year and support
natural grasslands.
Stolon. A horizontal stem that forms at ground level and gives rise to new tillers in
grasses.
Stoma or stomate. A tiny pore in the outer layer of a leaf through which gases, includ-
ing water vapor, are exchanged with the atmosphere. The plural is stomata.
Subshrub. A hard-stemmed shrub in which the upper branches die back during the non-
growing season. In a sense, a shrub that acts like a perennial forb.
Succulent. A growthform that permits the storage of water in some of its tissues. Plants
may be leaf succulents, stem succulents, or have special underground organs for
storing water.
Tiller. A daughter plant or new plantlet forming from a grass's stolons or rhizomes.
Trade Winds. The strong, constant easterly winds of tropical latitudes.
Tropics. The latitudinal zone on Earth that lies between 23 30 0 N and 23 30 0 S, that is,
between the Tropic of Cancer and the Tropic of Capricorn.
Tussock. A growthform of grasses and sedges in which individuals grow in clumps,
forming visible hummocks.
Ungulate. A hoofed mammal.
Vegetation. The general plant cover of an area described in terms of its structure and
appearance and not the species that comprise it.
Warm Season Grass. A grass that photosynthesizes and grows best under high temper-
ature conditions. These are C 4 grasses found in the tropics and in temperate grass-
lands with hot summers.
Weather. The state of the atmosphere at any given moment. Includes atmospheric
pressure, temperature, humidity, and type of precipitation (if any).
Weathered. Pertaining to bedrock that has undergone physical and/or chemical break-
down into small particles, even ions.
Weed. A plant adapted to invade disturbed sites. Generally short-lived, they are good
dispersers and fast growers.