Mammillaria Mound.

DP102-2013  Posted April 12; processed ditto.

Each cactus in the mound is fairly small, with each opened blossom no more than 1/4 - 1/2 inch across, I'd say.  The entire mound is several feet in diameter, at a guess.  The perspective of the shot exaggerates its size relative to, for example, the truly large variegated leaf century plant in the background.

Matthaei Botanical Gardens Conservatory,
April 10, 2013
Astrophytum Cactus #01b-2012M 05
Backlit spines on a star cactus.
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Arid House, Conservatory at the Matthaei Botanical Gardens, 
Ann Arbor, Michigan
November 1, 2012
Mount Lemmon Hwy or the E. Catalina Hwy begins its tortuous eastward route up the southern flanks of the Santa Catalina Mountains before turning northward toward Summerhaven and Mt. Lemmon itself.
(My main reason for taking this shot was to see whether our rental house would be visible in the shot.  It is.)
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Seen from Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)
Ho, ho, ho!
Mistletoe and Snow.
Makes the season jolly,
Don't you know.
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Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)
Northern Mockingbird (tentative ID) perched on ocotillo stems.
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Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)
Northern Mockingbird (tentative ID) perched on ocotillo stems.
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Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)
Impression of the Sonoran desert - conventional treatment of a wider view.
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Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)
Impression of the Sonoran desert - filtered treatment in portrait format.

Taken from the roadside, possibly even from the moving car.  The original was a flat, poorly focused image.  The angle of the light relative to our position, for one thing, and the time of day, for another, weren't conducive to a great shot.  But I liked the two large saguaros when I saw them, and I still like the overall composition of the shot.  So I fell back on pp'ing with some filters to make the image pop a little more and to make it obvious that I was going for an impression of the scene rather than a strict rendering of it.
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Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)
(For anyone interested, I used about equal amounts of the Photoshop Fresco and Sumi-e filters.)
Javelina Rocks

DP021-2013.  Posted January 21, 2013; processed Jan. 21.
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The location name, Javelina Rocks, describes an outcropping of Catalina gneiss that is frequented by javelinas.  The last major turnout on the park's loop drive is at this spot.  The gneiss in question formed from granite rather than from sedimentary rock.  Bright neon green lichen had colonized many of the surfaces.  I don't yet know the geologic history that tipped the layers of rock so steeply at this location.
Saguaro National Park, East.
Tucson, Arizona
December 20, 2012 (mid- to late morning)

Many thanks to all who left comments on the euphorbia picture, especially those who looked at both versions and expressed a preference one way or another.
Mammillaria Mound.

DP102-2013 Posted April 12; processed ditto.

Each cactus in the mound is fairly small, with each opened blossom no more than 1/4 - 1/2 inch across, I'd say. The entire mound is several feet in diameter, at a guess. The perspective of the shot exaggerates its size relative to, for example, the truly large variegated leaf century plant in the background.

Matthaei Botanical Gardens Conservatory,
April 10, 2013
Mammillaria Mound.

DP102-2013  Posted April 12; processed ditto.

Each cactus in the mound is fairly small, with each opened blossom no more than 1/4 - 1/2 inch across, I'd say.  The entire mound is several feet in diameter, at a guess.  The perspective of the shot exaggerates its size relative to, for example, the truly large variegated leaf century plant in the background.

Matthaei Botanical Gardens Conservatory,
April 10, 2013
Mammillaria Mound.

DP102-2013 Posted April 12; processed ditto.

Each cactus in the mound is fairly small, with each opened blossom no more than 1/4 - 1/2 inch across, I'd say. The entire mound is several feet in diameter, at a guess. The perspective of the shot exaggerates its size relative to, for example, the truly large variegated leaf century plant in the background.

Matthaei Botanical Gardens Conservatory,
April 10, 2013
See photo in original gallery.