Desert Spring

by Kathy Bassett

Title

Desert Spring

Artist

Kathy Bassett

Medium

Photograph - Photography - Collage

Description

Saguaro National Park is in southern Arizona. Its 2 sections are on either side of the city of Tucson. The park is named for the large saguaro cactus, native to its desert environment. In the western Tucson Mountain District, Signal Hill Trail leads to petroglyphs of the ancient Hohokam people.Some of the bird species include great horned owls, ravens, kestrels, turkey vultures, roadrunners, woodpeckers, hawks, quails, and hummingbirds In the eastern Rincon Mountain District, Cactus Forest Drive is a loop road with striking views of the desert landscapeGeometrics everywhere.SpinesBotanically, "spines" are distinguished from "thorns": spines are modified leaves, and thorns are modified branches. Cacti produce spines, always from areoles as noted above. Spines are present even in those cacti with leaves, such as Pereskia, Pereskiopsis and Maihuenia, so they clearly evolved before complete leaflessness. Some cacti only have spines when young, possibly only when seedlings. This is particularly true of tree-living cacti, such as Rhipsalis or Schlumbergera, but ground-living cacti, such as Ariocarpus, also lack spines when mature.The spines of cacti are often useful in identification, since they vary greatly between species in number, color, size, shape and hardness, as well as in whether all the spines produced by an areole are similar or whether they are of distinct kinds. Most spines are straight or at most slightly curved, and are described as hair-like, bristle-like, needle-like or awl-like, depending on their length and thickness. Some cacti have flattened spines (e.g. Schlerocactus papyracanthus). Other cacti have hooked spines. Sometimes, one or more central spines are hooked, while outer spines are straight (e.g., Mammillaria rekoi).In addition to normal-length spines, members of the subfamily Opuntioideae have relatively short spines, called glochids that are barbed along their length and easily shed. These enter the skin and are difficult to remove, causing long-lasting irritation.

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April 4th, 2017

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