We use the word "thorn" very generically to refer to any sharp pointy part of a plant. However, to be technically correct, there are three different types of sharp pointy things:
- Prickles are modified epidermal tissue. The epidermis is the surface layer of the stem. Prickles are found on many plants in the Rosaceae (Rose) Family, as well as other plants such as Greenbrier vine.
- Spines are modified leaf tissue. The sharp pointy things on cacti are spines. The sharp tips of Agarita leaves and the sharp projections along the margin of Sotol leaves are also spines.
- Then there are the true thorns. Thorns are modified branch tissue. They are essentially branches with sharp pointed tips. Numerous trees and shrubs have true thorns.
This is going to be a series of posts. Probably the best place to begin is with the Bluewood Condalia (Condalia hookeri). This Condalia generally grows as an understory shrub in wooded areas of the Texas Hill Country and to the south in the open brush throughout the South Texas Brush Country.
The leaves of Bluewood Condalia grow on twigs with a very sharp terminal thorn. This is by far one of the best examples demonstrating that thorns are in fact modified branches:
Lote-bush Condalia (Ziziphus obtusifolia) looks very similar to Bluewood Condalia and the two are easily confused. Their ranges overlap in Texas. While they are not in the same Genus, they are both in the Rhamnaceae (Buckthorn) Family. Both of these shrubs have leaves on twigs with terminal thorns. The Lotebush, as it is often called, has twigs with leaves as well as bare twigs both with terminal thorns.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Monday, October 28, 2013.
I have to give credit to Dr. Floyd Waller, my botanist friend and mentor, for the original inspiration for this series of posts.
Wednesday, February 13, 2013
McAllister Park, natural surface trail beside Mud Creek
downstream from Buckhorn Rd
Today's photos:
While the natural areas of McAllister Park suffer from even more of the stress that is common to most urban natural areas due to the fact that over the years the park has become a multi-use facility, it is still a prime example in San Antonio of a dynamic urban forest:
- The first photo is looking face to face at a red admiral butterfly. It was at the entrance to the trail and I had a strange feeling this butterfly was watching over the comings and goings on the trail.
- The second photo is a detail of a portion of a very large, decaying trunk of a fallen live oak tree. This trunk has been lying on the forest floor for at least a couple of years. Even though the tree is no longer living, its decaying trunk still plays a critical role in the ongoing life of the forest's biotic community.
- The third, fourth and fifth photo are of the berries remaining on a possumhaw bush. While its berries are a beautiful sight, it left me wondering why the frugivores haven't devoured them yet.
- The sixth photo is of a very large bluewood condalia bush. This one, by my estimate, is a good ten to twelve feet tall.
- The seventh photo is the top of one of the numerous very large and impressive live oaks that are growing in McAllister Park.
- The eighth and ninth photo are of a grey hairstreak (or one of its close hairstreak cousins) butterfly drinking nectar from agarita flowers.
- The tenth and eleventh photo are close ups of agarita flowers.
- The twelfth photo, like the seventh photo, is another live oak tree.
- The thirteenth, fourteenth and fifteenth photos are of a backlit American snout butterfly.
- The sixteenth and seventeenth photos are of a ruby-crowned kinglet. These birds do not sit still for more than a couple seconds at a time and are constantly flitting around a tree. This kinglet was finding plenty to eat in a hackberry thicket. The density of the tree branches and the way they intertwine made it even more difficult to get even a couple photos of this beautiful little bird.
- The eighteenth, nineteenth and twentieth photos are of another red admiral butterfly sunning itself on a fallen live oak limb. When this limb had fallen, it took part of a large grapevine with it.
Friday, January 25, 2013
Mud Creek Park
Today's photos:
The next park upstream along Mud Creek from McAllister Park is Mud Creek Park. Mud Creek Park is a 67 acre flood control retention basin and Edwards Aquifer recharge site with at least 1.4 miles of nature trails (pdf). This was the first time I have been to this park and I only walked a portion of the trail along the eastern most part of the loop trail.
The flora and fauna in this series of photos are too numerous to list all of them, but here are a few of the highlights: Whitethorn Acacia, Huisache, Live Oak, Ashe Juniper (a.k.a. Mountain Cedar), an Orange Sulphur butterfly, Spanish Dagger Yucca, Sotol, Twisted-leaf Yucca, a Black Vulture, Bluewood Condalia and Wafer Ash seeds.
There is one additional set of photos from this walk that will be featured in the upcoming Sunday Special Edition
Monday, December 17, 2012
Crescent Bend Nature Park
Today's photos:
The air was comfortably warm and the sky a bright winter blue this afternoon at Crescent Bend Nature Park. A distinctively sweet savanna aroma brought back memories of similar days in numerous other places from many decades ago. It is an aroma similar to fresh cut hay, but with an added woodland accent.
The winter hardy red admiral, American snout, orange sulphur and dainty sulphur butterflies flitted about. The red admirals and American snouts cooperated photographically. The sulphurs just wouldn't sit still long enough to get them into focus. There were also a wide variety of birds. I'll post their photos tomorrow.
As I pointed out in my post from August 1, 2011, Crescent Bend Nature Park is a section of land that is being returned from development to a natural savanna habitat. The ecosystem recovery and improvement in wildlife habitat over just the past sixteen months has been remarkable. Nature is quite resilient and can heal itself when given an adequate amount of protection.
