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from article Mustard
Black mustard (Brassica nigra). (Photo courtesy of Jennifer Anderson, USDA–NRCS PLANTS Database)
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from article Acanthodii
Jaws of an Early Devonian ischnacanthid from northern Canada. The upper palatoquadrate and lower meckelian cartilages have tooth-bearing jawbones along their facing edges. (From University of Alberta, Laboratory for Vertebrate Paleontology…
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from article Acanthodii
Examples of acanthodians from the Early Devonian of northern Canada. (a) Primitive climatiiform Lupopsyrus. (b) Diplacanthid Tetanopsyrus. (c) Ischnacanthiform Ischnacanthus. (d) Unnamed mesacanthid acanthodiform. (From the University of Alberta,…
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from article Asian vegetables
A head of Chinese cabbage. (Credit: Jiang Hongyan/Shutterstock)
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from article Asian vegetables
Bok choy, also known as pak choy or Chinese mustard. (Credit: Agricultural Research Service, U.S. Department of Agriculture)
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from article Asian vegetables
Daikon (oriental winter radish) is a notable vegetable in Japan. (Credit: Franco Folini)
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from article Asian vegetables
Mung bean sprouts.
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from article Asian vegetables
Chinese okra. The length of the fruit can reach 30–38 cm (12–15 in.). (Credit: Forest and Kim Starr)
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from article Lichens
The ascolichen Teloschistes chrysophthalmus. (Credit: Jason Hollinger)
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from article Lichens
Cuplike lichens of the genus Cladonia. (Credit: Jacinta Lluch Valero)
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from article Ebony
Persimmon (Diospyros virginiana). (Photograph by Dot Paul, National Resources Conservation Service, USDA)
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from article Tangerine
Tangerine fruits (Citrus reticulata). (Photo by Forest and Kim Starr)
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from article Dune vegetation
A coastal dune profile.
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from article Dune vegetation
American beachgrass (Ammophila breviligulata), which dominates coastal dunes along much of the Eastern seaboard of the United States and the Great Lakes. (Photo by Rob Routledge, Sault College, Sault Ste. Marie, Ontario, Canada)
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from article Dune vegetation
Sea oats (Uniola paniculata) are abundant on the foredunes of the Atlantic coast of the southeastern United States. (Photo by Robert L. Anderson, USDA Forest Sevice)
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from article Dune vegetation
Bitter panicum (bitter panicgrass; Panicum amarum), which is often found on Gulf of Mexico coastal dunes. (Photo by Forest and Kim Starr)
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from article Index fossil
Three cephalopod genera forming an evolutional sequence. Their short ranges (indicated by bars) and distinctive suture lines (the area between two sutures is shown in black) make them ideal index fossils for the early Pennsylvanian Period. (After A.…
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from article Index fossil
Different concepts of range zones based on various combinations of overlap of two or more index species. (From D. R. Prothero and F. Schwab, Sedimentary Geology: An introduction to Sedimentary Rocks, Freeman, 1996)
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from article Index fossil
Potential range versus actual range of an index fossil species. Note that the actual time of occurrence at a given locality is generally some fraction of the actual range of the species because of the limitations of environment, immigration, and…
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from article Index fossil
Graphic correlation method of Alan Shaw. Note that the X and Y axes of the graphs are scaled diagrams of measured sections of the two different outcrops to be correlated. The points plotted on the graphs are the corresponding heights of the first or…
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from article Forage crops
Bahia grass (Paspalum notatum), a popular warm-season grass used as a forage crop. (Photo by James H. Miller and Ted Bodner, Southern Weed Society)
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from article Forage crops
Alfalfa (Medicago sativa), the most important legume forage crop, cut and drying prior to its final harvest. (Photo by Howard F. Schwartz, Colorado State University)
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from article Nitrogen-fixing trees
Nitrogen-fixing Rhizobium bacteria form nodules on the roots of various legume trees. (Copyright © McGraw Hill)
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from article Nitrogen-fixing trees
A perennial nodule, several years old, formed on the roots of common or black alder (Alnus glutinosa) by symbiosis with Frankia (a nitrogen-fixing bacterium). (Copyright © McGraw Hill)
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from article Earth rotation and orbital motion
Excess length of day [length of day − 86,400 atomic Système International (SI) seconds], measured in milliseconds.
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from article Earth rotation and orbital motion
Couple produced by tidal friction.
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from article Earth rotation and orbital motion
Schematic representation of the Earth's orbit.
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from article Earth rotation and orbital motion
Equation of time.
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from article Earth rotation and orbital motion
Precession/nutation and polar motion.
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from article Wheat
A sheaf of wheat (Triticum) surrounded by some small piles of seed (grain). (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)
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from article Wheat
A combined harvester-thresher is used to harvest wheat. (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)
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from article Wheat
Adaptation regions for wheat in the United States. (Credit: U.S. Department of Agriculture)
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from article Wheat
Wheat (Triticum) growing in a field. The wheat inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag rachis (main axis). (Credit: Tim McCabe/Natural Resources Conservation Service, U.S. Department of Agriculture)
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from article Wheat
Black stem rust of wheat, which produces urediniospores in reddish-brown pustules. The fungus Puccinia graminis f. sp. tritici is responsible for this plant disease. The inset shows a close-up view of an infected stem. (Credit: Agricultural Research…
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from article Wheat
Loose smut of wheat, caused by Ustilago tritici. (Credit: Erik Stromberg/Virginia Polytechnic Institute and State University)
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from article Anthropocene extinction
The relationship between species extinctions and the human population on Earth since the year 1800. As the human population has increased, so too have the numbers of species extinctions. The numbers have been so great that the current Anthropocene…
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from article Permian
Permian, the sixth period of the Paleozoic.
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from article Permian
Correlation of major Permian rock units.
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from article Permian
East-west section of the Permian System in its type area.
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from article Permian
Depositional and structural relationships in western Texas during Permian time.
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from article Permian
Section across the Capitan Reef Complex. 1 m = 3.3 ft; 1 km = 0.6 mi.
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from article Permian
Paleogeography during the earliest part of the Permian Period.
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from article Permian
Paleogeography near the middle of the Permian Period.
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from article Ginger
Ginger (Zingiber officinale). (USDA)
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from article Reforestation
Forests and people in the world.
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from article Reforestation
Relative amounts of land needed to produce 1000 ft3 of wood per year. (1) Mature, upland, natural hardwood stand. (2) Pine plantation owned by a farmer and managed with minimum inputs. (3) Pine plantation managed by a forest company and managed with…
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from article Gastornithiformes
Gastornis giganteus (reconstruction), an extinct flightless bird belonging to the order Gastornithiformes. (Photo courtesy of the American Museum of Natural History, New York)
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from article Gaviiformes
Common loon (Gavia immer) at Jammer Lake, Minnesota. (Photograph copyright © DonGettyPhoto.com)
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from article Guava
Fruit and leaves of the guava (Psidium guajava). (Photo courtesy of Forest and Kim Starr)
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from article Tupelo
Leaves of black tupelo (Nyssa sylvatica). (Photograph courtesy of Larry Allain, USGS National Wetlands Research Center)
