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from article Pyroclastic rocks
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Image
from article Pyroclastic rocks
Distribution downwind of the pyroclastic fall deposit from the climactic eruption of Mount St. Helens, Washington, on May 18, 1980. The contours (isopachs) are drawn through points of measured equal thickness (in centimeters) of this ash layer.…
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from article Pyroclastic rocks
Aerial view in March 1998 of the fan-shaped pyroclastic delta formed by repeated entries of pyroclastic flows and surges into the Caribbean Sea during the Soufrière Hills Volcano eruption in 1996–1997. (Photograph by R.P. Hoblitt, USGS)
Image
from article Pyroclastic rocks
Observed or postulated mechanisms for the generation of pyroclastic flow and surge deposits (from W. E. Scott, 1989). (a, b) Mechanisms that commonly produce block-and-ash flow deposits. (b, c) Mechanisms that trigger laterally directed blasts.…
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from article Pyroclastic rocks
Some variations in pyroclastic rock formations. (a) Layers of pyroclastic fall deposits from the eruption plume of the June 15, 1991, explosive eruption of Mount Pinatubo (Luzon, Philippines). This exposure, located about 9 km (5.5 mi) southeast of…
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from article Equisetales
Equisetum arvense. (a) Sterile shoot. (b) Fertile shoot growing from an underground rootstock. (c) Cone. (d) Two views of shield-shaped sporangiophores. (e) Spores, greatly enlarged. As spore dries, elaters expand. (After E. W. Sinnott and K. S.…
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from article Equisetales
Equisetum gametophyte. (a) Small gametophyte, showing antheridia only. (b) Male gametes. (c) Larger gametophyte; branching lobes have archegonia at bases. (After E. W. Sinnott and K. S. Wilson, Botany: Principles and Problems, 6th ed., McGraw-Hill,…
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from article Equisetales
Sporophytes. (a) Equisetum gametophyte with sporophytes. (b, c, d) The young sporophytes of Equisetum hiemale. (After G. M. Smith, Cryptogamic Botany, vol. 2, 2d ed., McGraw-Hill, 1955)
Image
from article Pathotoxin
Oat seedling resistant to Victoria blight obtained by screening a susceptible population with the pathotoxin victorin, a product of the pathogen Helminthosporium victoriae.
Image
from article Pathotoxin
Separation of corn seedlings resistant (N) and susceptible (T) to southern corn leaf blight by treatment with a pathotoxin produced by Helminthosporium maydis race T.
