Thorn trees
Acacia
Summary 6
Acacia (/əˈkeɪʃə/ or /əˈkeɪsiə/), also known as a thorntree, whistling thorn or wattle, is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, described by the Swedish botanist Carl Linnaeus in 1773 based on the African species Acacia nilotica. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. All species are pod-bearing, with sap and leaves often bearing large amounts of tannins and condensed...
Description 7
Trees or shrubs, sometimes climbing, armed with thorns (native spp.) or unarmed (introduced spp.). Leaves alternate, 2-pinnate or (in some introduced spp.) modified to phyllodes and thus appearing to have simple leaves. Pinnae opposite, subopposite, sometimes alternate. Gland usually present on the upper side of the petiole, sometimes also glands on the rhachis. Inflorescences usually axillary, racemose or paniculate; flowers in elongated spikes or spherical heads, bisexual or unisexual. Calyx gamosepalous, subtruncate or with 4-5 lobes. Corolla 4-5(-7)-lobed. Stamens numerous. Anthers glandular or eglandular. Pod very variable, dehiscent or indehiscent. An important genus, occurring commonly in a wide range of habitats. A careful distinction should be made between the stipules which in some species are modified into straight spines arising from near the leaf base and prickles, which are usually curved and are usually found near the nodes but may occur along the stems. Some acacias, especially older trees, may be unarmed, which can be very puzzling. It is recommended that a careful search is made of the tree (if possible) or of similar trees in the area. An important general rule with acacias is that those with straight spines (stipules) have flowers in spherical heads and those with curved prickles have flowers in spikes. The exceptions are: Faidherbia albida has straight spines and flowers in spikes. Acacia mellifera has curved prickles but the flower spike is so short as to appear almost spherical. Acacia schweinfurthii has curved prickles and flowers in spherical heads. Acacia tortilis has both curved prickles and straight spiny stipules and flowers in spherical heads.
Sources and Credits
- (c) Justin Hall, some rights reserved (CC BY), http://www.flickr.com/photos/35034345586@N01/360325085
- (c) Steven J. Baskauf, some rights reserved (CC BY), http://bioimages.vanderbilt.edu/baskauf/14869
- (c) Tony Rodd, some rights reserved (CC BY-NC-SA), http://farm4.static.flickr.com/3354/3594172806_3f23efbdbb.jpg
- (c) Mike, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Acacia_farnesiana_az.jpg/460px-Acacia_farnesiana_az.jpg
- (c) Donald Hobern, some rights reserved (CC BY), http://farm6.static.flickr.com/5161/5365632758_0027a56981.jpg
- (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Acacia
- (c) Mark Hyde, Bart Wursten and Petra Ballings, some rights reserved (CC BY-NC), http://eol.org/data_objects/19229780
