Acacia  

Acacia (pronounced /əˈkeɪʃə/) is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. They are pod-bearing, with sap and leaves typically bearing large amounts of tannins and condensed tannins that historically in many species found use as pharmaceuticals and preservatives.

The generic name derives from ακακία (akakia), the name given by early Greek botanist-physician Pedanius Dioscorides (ca. 40-90) to the medicinal tree A. nilotica in his book Materia Medica.^[2] This name derives from the Greek word for its characteristic thorns, ακις (akis, thorn).^[3] The species name nilotica was given by Linnaeus from this tree's best-known range along the Nile river.

Acacias are also known as thorntrees, whistling thorns or wattles, including the yellow-fever acacia and umbrella acacias.

Until 2005, there were thought to be roughly 1300 species of acacia worldwide, about 960 of them native to Australia, with the remainder spread around the tropical to warm-temperate regions of both hemispheres, including Europe, Africa, southern Asia, and the Americas. However, the genus was then divided into five, with the name Acacia retained for the Australian species (and a few in tropical Asia, Madagascar and Pacific Islands), and most of the species outside Australia divided into Vachellia and Senegalia. The two final genera, Acaciella and Mariosousa, only contain about a dozen species from the Americas each.

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Classification

Acacia pycnantha

Acacia berlandieri

Acacia smallii

The genus Acacia is evidently not monophyletic. This discovery has led to the breaking up of Acacia into five new genera as discussed in: List of Acacia species. In common parlance, the term "acacia" is occasionally misapplied to species of the genus Robinia, which also belongs in the pea family. Robinia pseudoacacia, an American species locally known as Black Locust, is sometimes called "false acacia" in cultivation in the United Kingdom.

Geography

The southernmost species in the genus are Acacia dealbata (Silver Wattle), Acacia longifolia (Coast Wattle or Sydney Golden Wattle), Acacia mearnsii (Black Wattle), and Acacia melanoxylon (Blackwood), reaching 43°30' S in Tasmania, Australia, while Acacia caven (Espinillo Negro) reaches nearly as far south in northeastern Chubut Province of Argentina. Australian species are usually called wattles, while African and American species tend to be known as acacias.

Acacia retinodes

Acacia albida, Acacia tortilis and Acacia iraqensis can be found growing wild in the Sinai desert and the Jordan valley. It is found in the savanna vegetation of the tropical continental climate. It grows wild in Montserrat West Indies; there it is locally referred to as 'cusha.'

Description

The leaves of acacias are compound pinnate in general. In some species, however, more especially in the Australian and Pacific islands species, the leaflets are suppressed, and the leaf-stalks (petioles) become vertically flattened, and serve the purpose of leaves. These are known as phyllodes. The vertical orientation of the phyllodes protects them from intense sunlight, as with their edges towards the sky and earth they do not intercept light so fully as horizontally placed leaves. A few species (such as Acacia glaucoptera) lack leaves or phyllodes altogether, but possess instead cladodes, modified leaf-like photosynthetic stems functioning as leaves.

Acacia dealbata

The small flowers have five very small petals, almost hidden by the long stamens, and are arranged in dense globular or cylindrical clusters; they are yellow or cream-colored in most species, whitish in some, even purple (Acacia purpureapetala) or red (Acacia leprosa Scarlet Blaze). Acacia flowers can be distinguished from those of a large related genus, Albizia, by their stamens which are not joined at the base. Also, unlike individual Mimosa flowers, those of Acacia have more than 10 stamens.^[4]

The plants often bear spines, especially those species growing in arid regions. These sometimes represent branches which have become short, hard and pungent, or sometimes leaf-stipules. Acacia armata is the Kangaroo-thorn of Australia and Acacia erioloba is the Camelthorn of Africa.

Acacia seeds can be difficult to germinate. Research has found that immersing the seeds in various temperatures (usually around 80 °C) and manual seed coat chipping can improve yields to approximately 80 percent.^[5]

Symbiosis

Acacia collinsii Thorns

In the Central American Acacia sphaerocephala, Acacia cornigera, and Acacia collinsii (collectively known as the bullthorn acacias), the large thorn-like stipules are hollow and afford shelter for several species of Pseudomyrmex ants, which feed on a secretion of sap on the leaf-stalk and small, lipid-rich food-bodies at the tips of the leaflets called Beltian bodies. In return, the ants add protection to the plant against herbivores.^[6] Some species of ants will also fight off competing plants around the acacia, cutting off the offending plant's leaves with their jaws and ultimately killing it. Other associated ant species appear to do nothing to benefit their hosts.

Similar mutualisms with ants occur on Acacia trees in Africa, such as the Whistling Thorn acacia. The acacias provide shelter for ants in the thorns and nectar in extrafloral nectaries for their symbiotic ants such as Crematogaster mimosae. In turn, the ants protect the plant by attacking large mammalian herbivores and stem-boring beetles that damage the plant.

Pests

In Australia, Acacia species are sometimes used as food plants by the larvae of hepialid moths of the genus Aenetus including A. ligniveren. These burrow horizontally into the trunk then vertically down. Other Lepidoptera larvae which have been recorded feeding on Acacia include Brown-tail, Endoclita malabaricus and Turnip Moth. The leaf-mining larvae of some bucculatricid moths also feed on Acacia: Bucculatrix agilis feeds exclusively on Acacia horrida and Bucculatrix flexuosa feeds exclusively on Acacia nilotica.

Acacias contain a number of organic compounds that defend them from pests and grazing animals.^[7]

Uses

Food uses

Acacia seed pods, also known as Guajes, served as part of a botana in Oaxaca, Mexico.

Acacia seeds in the Negev, Israel.

Acacia seeds are often used for food and a variety of other products.

In Burma, Laos and Thailand, the feathery shoots of Acacia pennata (common name cha-om, ชะอม and su pout ywet in Burmese) are used in soups, curries, omelettes, and stir-fries.

Honey made by bees using the acacia flower as forage is considered a delicacy, appreciated for its mild flowery taste, soft running texture and glass-like appearance. Acacia honey is one of the few honeys which does not crystallize.^[8]
In Mexico the seeds are known as Guajes. Guajes or huajes are the flat, green pods of an acacia tree. The pods are sometimes light green or deep red in color—both taste the same. Guaje seeds are about the size of a small lima bean and are eaten raw with guacamole, sometimes cooked and made into a sauce. They can also be made into fritters. The ground seeds are used to impart a slightly garlicy flavor to a mole called guaxmole (huaxmole). The dried seeds may be toasted and salted and eaten as a snack referred to as "cacalas". Purchase whole long pods fresh or dried at Mexican specialty markets.

The first-known predominantly vegetarian spider Bagheera kiplingi, which is found in Central America and Mexico, was first documented and filmed in 2009 feeding from the tips of the acacia plants which are known as Beltian bodies which contain high concentrations of protein. All other 40,000 known species of spider's diets are mainly believed to be carnivorous.

Acacia is listed as an ingredient in Sun Drop, Fresca, a citrus soft drink, RC Cola, Barq's root beer, Full Throttle Unleaded Energy Drink, Strawberry-Lemonade Powerade^[9] as well as in Läkerol pastille candies, Altoids mints, Langer's Pineapple coconut Juice, Wrigley's Eclipse chewing gum and M&Ms Pretzel.

Gum

Various species of acacia yield gum. True gum arabic is the product of Acacia senegal, abundant in dry tropical West Africa from Senegal to northern Nigeria.

Acacia arabica is the gum-Arabic tree of India, but yields a gum inferior to the true gum-Arabic.

Acacia covenyi

Medicinal uses

Many Acacia species have important uses in traditional medicine. Most of the uses have been shown to have a scientific basis since chemical compounds found in the various species have medicinal effects.^{[citation needed]}

In Ayurvedic medicine, Acacia nilotica is considered a remedy that is helpful for treating premature ejaculation. A 19th century Ethiopian medical text describes a potion made from an Ethiopian species of Acacia (known as grar) mixed with the root of the tacha, then boiled, as a cure for rabies.^[10]

An astringent medicine high in tannins, called catechu or cutch, is procured from several species, but more especially from Acacia catechu, by boiling down the wood and evaporating the solution so as to get an extract.^[11]

Ornamental uses

A few species are widely grown as ornamentals in gardens; the most popular perhaps is Acacia dealbata (Silver Wattle), with its attractive glaucous to silvery leaves and bright yellow flowers; it is erroneously known as "mimosa" in some areas where it is cultivated, through confusion with the related genus Mimosa.

Another ornamental acacia is Acacia xanthophloea (Fever Tree). Southern European florists use Acacia baileyana, Acacia dealbata, Acacia pycnantha and Acacia retinodes as cut flowers and the common name there for them is mimosa.^[12]

Ornamental species of acacia are also used by homeowners and landscape architects for home security. The sharp thorns of some species deter unauthorized persons from entering private properties, and may prevent break-ins if planted under windows and near drainpipes. The aesthetic characteristics of acacia plants, in conjunction with their home security qualities, makes them a considerable alternative to artificial fences and walls.

Paints

The ancient Egyptians used Acacia in paints.^[13]

Perfume

Acacia farnesiana

Acacia farnesiana is used in the perfume industry due to its strong fragrance. The use of Acacia as a fragrance dates back centuries. In the Bible, burning of acacia wood as a form of incense is mentioned several times.

Symbolism and ritual

The Acacia is used as a symbol in Freemasonry, to represent purity and endurance of the soul, and as funerary symbolism signifying resurrection and immortality. The tree gains its importance from the description of the burial of Hiram Abiff, the builder of King Solomon's Temple in Jerusalem.

Several parts (mainly bark, root and resin) of Acacia are used to make incense for rituals. Acacia is used in incense mainly in India, Nepal, and China including in its Tibet region. Smoke from Acacia bark is thought to keep demons and ghosts away and to put the gods in a good mood. Roots and resin from Acacia are combined with rhododendron, acorus, cytisus, salvia and some other components of incense. Both people and elephants like an alcoholic beverage made from acacia fruit.^[14] According to Easton's Bible Dictionary, the Acacia tree may be the “burning bush” (Exodus 3:2) which Moses encountered in the desert.^[15] Also, when God gave Moses the instructions for building the Tabernacle, he said to "make an ark of acacia wood" and "make a table of acacia wood" (Exodus 25:10 & 23, Revised Standard Version)

In Russia, Italy and other countries it is customary to present women with yellow mimosas (among other flowers) on International Women's Day (March 8). These "mimosas" are actually from Acacia dealbata (Silver Wattle).

Tannin

A bottle of tannic acid.

The bark of various Australian species, known as wattles, is very rich in tannin and forms an important article of export; important species include Acacia pycnantha (Golden Wattle), Acacia decurrens (Tan Wattle), Acacia dealbata (Silver Wattle) and Acacia mearnsii (Black Wattle).

Black Wattle is grown in plantations in South Africa. Most Australian acacia species introduced to South Africa have become an enormous problem, due to their naturally aggressive propagation. The pods of Acacia nilotica (under the name of neb-neb), and of other African species are also rich in tannin and used by tanners.

Wood

Acacia koa Wood

Acacia tree near the end of its range in the Negev Desert of southern Israel.

Some Acacia species are valuable as timber, such as Acacia melanoxylon (Blackwood) from Australia, which attains a great size; its wood is used for furniture, and takes a high polish; and Acacia omalophylla (Myall Wood, also Australian), which yields a fragrant timber used for ornaments. Acacia seyal is thought to be the Shittah-tree of the Bible, which supplied shittim-wood. According to the Book of Exodus, this was used in the construction of the Ark of the Covenant. Acacia koa from the Hawaiian Islands and Acacia heterophylla from Réunion island are both excellent timber trees. Depending on abundance and regional culture, some Acacia species (e.g. Acacia fumosa), are traditionally used locally as firewoods.^[19]

Acacia heterophylla Wood

In Indonesia (mainly in Sumatra) and in Malaysia (mainly in Sarawak) plantations of Acacia mangium are being established to supply pulpwood to the paper industry.

Land Reclamation

Acacia can be planted for erosion control, especially after mining or construction damage.^[24]

Ecological invasion

For the same reasons it is favored as an erosion-control plant, with its easy spreading and resilience, some varieties of acacia, namely Acacia mearnsii, are potentially an invasive species. Introduced worldwide it has become an invasive plant which is taking over grasslands and the abandoned agricultural areas, especially in moderate coastal and island regions where mild climate propagates its spreading. Australian/New Zealand Weed Risk Assessment gives it a "high risk, score of 15" rating and it is considered one of the world's 100 most invasive species.^[25] Extensive ecological studies should be performed before further introduction of acacia varieties as this fast-growing plant, once introduced, spreads fast and is extremely difficult to eradicate.

Phytochemistry of Acacia

Alkaloids

Egyptian goddess Isis

As mentioned previously, Acacias contain a number of organic compounds that defend them from pests and grazing animals.^[7] Many of these compounds are psychoactive in humans. The alkaloids found in Acacias include dimethyltryptamine (DMT), 5-methoxy-dimethyltryptamine (5-MeO-DMT) and N-methyltryptamine (NMT). The plant leaves, stems and/or roots are sometimes made into a brew together with some MAOI-containing plant and consumed orally for healing, ceremonial or religious uses. Egyptian mythology has associated the acacia tree with characteristics of the tree of life (see the article on the Myth of Osiris and Isis).

Acacias Known to Contain Psychoactive Alkaloids

Acacia acuminata	Up to 1.5% alkaloids, mainly consisting of tryptamine in leaf[26]
Acacia adunca	β-methyl-phenethylamine, 2.4% in leaves[27]
Acacia alpina	Active principles in leaf[28]
Acacia aneura	Ash used in Pituri.[29] Ether extracts about 2-6% of the dried leaf mass.[30] Not known if psychoactive per se.
Acacia angustissima	β-methyl-phenethylamine,[31] NMT and DMT in leaf (1.1-10.2 ppm)[32]
Acacia aroma	Tryptamine alkaloids.[33] Significant amount of tryptamine in the seeds.[34]
Acacia auriculiformis	5-MeO-DMT in stem bark[35]
Acacia baileyana	0.02% tryptamine and β-carbolines, in the leaf, Tetrahydroharman[28][36][37]
Acacia beauverdiana	Psychoactive[38] Ash used in Pituri.[29]
Acacia berlandieri	DMT, amphetamines, mescaline, nicotine[39]
Acacia catechu	DMT[40] and other tryptamines in leaf, bark
Acacia caven	Tryptamines
Acacia chundra	DMT and other tryptamines in leaf, bark
Acacia colei	DMT[41]
Acacia complanata	0.3% alkaloids in leaf and stem, almost all N-methyl-tetrahydroharman, with traces of tetrahydroharman, some of tryptamine[42][43][44]
Acacia concinna	Nicotine[45]
Acacia confusa	DMT & NMT in leaf, stem & bark 0.04% NMT and 0.02% DMT in stem.[28] Also N,N-dimethyltryptamine N-oxide[46]
Acacia constricta	β-methyl-phenethylamine[31]
Acacia coriacea	Ash used in Pituri.[29][47] Not known if psychoactive.
Acacia cornigera	Psychoactive,[47] Tryptamines[14]
Acacia cultriformis	Tryptamine, in the leaf, stem[28] and seeds.[34] Phenethylamine in leaf and seeds[34]
Acacia cuthbertsonii	Psychoactive[38]
Acacia delibrata	Psychoactive[38]
Acacia falcata	Psychoactive,[38] but less than 0.02% alkaloids[37]
Acacia farnesiana	Traces of 5-MeO-DMT[48] in fruit. β-methyl-phenethylamine, flower.[49] Ether extracts about 2-6% of the dried leaf mass.[30] Alkaloids are present in the bark[50] and leaves.[51] Amphetamines and mescaline also found in tree.[14]
Acacia filiciana	Added to Pulque, but not known if psychoactive[47]
Acacia floribunda	Tryptamine, phenethylamine,[52] in flowers[34] other tryptamines, phenethylamines[53]
Acacia greggii	N-methyl-β-phenethylamine,[31]phenethylamine[7]
Acacia harpophylla	Phenethylamine, hordenine at a ratio of 2:3 in dried leaves, 0.6% total[27]
Acacia holoserica	Hordenine, 1.2% in bark[27]
Acacia horrida	Psychoactive[47]
Acacia implexa	Psychoactive[54]
Acacia jurema	DMT, NMT
Acacia karroo	Psychoactive
Acacia kempeana	Used in Pituri, but not known if psychoactive.[47]
Acacia kettlewelliae	1.5[27]-1.88%[55] alkaloids, 92% consisting of phenylethylamine.[27] 0.9% N-methyl-2- phenylethylamine found a different time.[27]
Acacia laeta	DMT, in the leaf[28]
Acacia lingulata	Used in Pituri, but not known if psychoactive.[47]
Acacia longifolia	0.2% tryptamine in bark, leaves, some in flowers, phenylethylamine in flowers,[52] 0.2% DMT in plant.[56] Histamine alkaloids.[37]
Acacia longifoliavar. sophorae	Tryptamine in leaves, bark[34]
Acacia macradenia	Tryptamine[34]
Acacia maidenii	0.6% NMT and DMT in about a 2:3 ratio in the stem bark, both present in leaves[28]
Acacia mangium	Psychoactive[47]
Acacia melanoxylon	DMT, in the bark and leaf,[57] but less than 0.02% total alkaloids[37]
Acacia mellifera	DMT, in the leaf[28]
Acacia nilotica	DMT, in the leaf[28]
Acacia niloticasubsp. adstringens	Psychoactive, DMT in the leaf
Acacia obtusifolia	Tryptamine, DMT, NMT, other tryptamines,[58] 0.4-0.5% in dried bark, 0.07% in branch tips.[59]
Acacia oerfota	Less than 0.1% DMT in leaf,[36][60] NMT
Acacia penninervis	Psychoactive[38]
Acacia phlebophylla	0.3% DMT in leaf, NMT[28]
Acacia podalyriaefolia	Tryptamine in the leaf,[28] 0.5% to 2% DMT in fresh bark, phenethylamine, trace amounts[52]
Acacia polyacantha	DMT in leaf[28] and other tryptamines in leaf, bark
Acacia polyacanthassp. campylacantha	Less than 0.2% DMT in leaf, NMT; DMT and other tryptamines in leaf, bark[61]
Acacia prominens	Phenylethylamine, β-methyl-phenethylamine[27][52]
Acacia pruinocarpa	Ash used in Pituri.[29][47] Not known if psychoactive.
Acacia pycnantha	Ash used in Pituri,[47] but less than 0.02% total alkaloids.[37] Not known if psychoactive.
Acacia retinodes	DMT, NMT,[62] nicotine,[14] but less than 0.02% total alkaloids found[37]
Acacia rigidula	DMT, NMT, tryptamine, amphetamines, mescaline, nicotine and others[63]
Acacia roemeriana	β-methyl-phenethylamine[31]
Acacia rose	Acacia rose blooming in the garden.[28]
Acacia salicina	Ash used in Pituri.[29][47] Not known if psychoactive.
Acacia sassa	Psychoactive[47]
Acacia schaffneri	β-methyl-phenethylamine, Phenethylamine[7] Amphetamines and mescaline also found.[14]
Acacia schottii	β-methyl-phenethylamine[31]
Acacia senegal	Less than 0.1% DMT in leaf,[28] NMT, other tryptamines. DMT in plant,[49] DMT in bark.[34]
Acacia seyal	DMT, in the leaf.[28] Ether extracts about 1-7% of the dried leaf mass.[30]
Acacia sieberiana	DMT, in the leaf[28]
Acacia simplex	DMT and NMT, in the leaf, stem and trunk bark, 0.81% DMT in bark, MMT[28][64]
Acacia taxensis	β-methyl-phenethylamine[31]
Acacia tortilis	DMT, NMT, and other tryptamines[58]
Acacia vestita	Tryptamine, in the leaf and stem,[28] but less than 0.02% total alkaloids[37]
Acacia victoriae	Tryptamines, 5-MeO-alkyltryptamine[34]

List of acacia species having little or no alkaloids in the material sampled:^[37]

0% C 0.02%, C...Concentration of Alkaloids [%]

• Acacia acinacea
• Acacia baileyana
• Acacia decurrens
• Acacia dealbata
• Acacia mearnsii
• Acacia drummondii
• Acacia elata
• Acacia falcata
• Acacia leprosa
• Acacia linearis
• Acacia melanoxylon
• Acacia pycnantha
• Acacia retinodes
• Acacia saligna
• Acacia stricta
• Acacia verticillata
• Acacia vestita

Cyanogenic glycosides

Nineteen different species of Acacia in the Americas contain cyanogenic glycosides, which, if exposed to an enzyme which specifically splits glycosides, can release hydrogen cyanide (HCN) in the acacia "leaves."^[65] This sometimes results in the poisoning death of livestock.

If fresh plant material spontaneously produces 200 ppm or more HCN, then it is potentially toxic. This corresponds to about 7.5 μmol HCN per gram of fresh plant material. It turns out that, if acacia "leaves" lack the specific glycoside-splitting enzyme, then they may be less toxic than otherwise, even those containing significant quantities of cyanic glycosides.^[37]

Some Acacia species containing cyanogens:

• Acacia erioloba
• Acacia cunninghamii
• Acacia obtusifolia
• Acacia sieberiana
• Acacia sieberiana var. woodii^[66]

Species

There are over 1,300 species of Acacia. See List of Acacia species for a more complete listing.

Famous acacia

Perhaps the most famous acacia is the Arbre du Ténéré in Niger. The reason for the tree's fame is that it used to be the most isolated tree in the world, approximately 400 km (249 mi) from any other tree. The tree was knocked down by a truck driver in 1973.

Identification gallery

Flowers

Acacia aneura	Acacia catechu	Acacia baileyana	Acacia berlandieri
Acacia confusa	Acacia constricta, Las Vegas, Nevada, USA	Acacia covenyi	Acacia dealbata
Acacia denticulosa	Acacia drummondii	Acacia erioloba Sossusvlei, Namibia	Acacia fimbriata Australian National Botanic Gardens, Canberra
Acacia heterophylla	Acacia longifolia	Acacia melanoxylon Nazaré, Portugal	Acacia saligna Side, Turkey
Acacia schinoides Australian National Botanic Gardens	Acacia tetragonophylla Geelong Botanic Gardens, Victoria, Australia	Acacia pennata in Talakona forest, in Chittoor District of Andhra Pradesh, India	Acacia pennata at Ananthagiri Hills, in Rangareddy district of Andhra Pradesh, India.

Bark

Acacia aneura Bark	Acacia auriculiformisBark	Acacia berlandieri Bark	Acacia collinsii Bark
Acacia confusa Bark, Hawaii, USA	Acacia dealbata	Acacia decurrens	Acacia erioloba
Acacia estrophiolataBark	Acacia greggii Bark	Acacia heterophyllaBark	Acacia pennata trunk in Talakona forest, in Chittoor District of Andhra Pradesh, India.

Foliage

Acacia catechu	Acacia collinsii Foliage	Acacia concinna Foliage	Acacia denticulosa Foliage
Acacia karroo Foliage	Acacia leprosa Foliage	Acacia pennata in Talakona forest, in Chittoor District of Andhra Pradesh, India.	Acacia pennata at Ananthagiri Hills, in Rangareddy district of Andhra Pradesh, India.

Seed pods

Acacia aneura	Acacia catechu	Acacia confusa	Acacia constricta
Acacia dealbata	Acacia heterophylla	Acacia melanoxylon

Seeds

Acacia baileyana	Acacia berlandieri	Acacia confusa	Acacia constricta
Acacia cyclops	Acacia dealbata	Acacia decurrens	Acacia farnesiana
Acacia greggii	Acacia longifolia	Acacia mearnsii	Acacia melanoxylon
Acacia pycnantha	Acacia rigidula	Acacia tortuosa

Thorns

Acacia catechu	Acacia collinsii	Acacia cornigera	Acacia horrida
Acacia farnesiana var. farnesiana	Acacia pennata in Talakona forest, in Chittoor District of Andhra Pradesh, India.

Tree

Acacia aneura	Acacia berlandieri	Acacia confusa	Acacia constricta
Acacia dealbata	Acacia heterophylla	Acacia koa	Acacia leprosa

Wood

Acacia koa

Acacia heterophylla

Acacia schaffneri

See also

• List of Acacia species
• Plant defense against herbivory
• Psychedelic plants

Notes

General references

• Clement, B.A., Goff, C.M., Forbes, T.D.A. Toxic Amines and Alkaloids from Acacia rigidula, Phytochem. 1998, 49(5), 1377.
• Shulgin, Alexander and Ann, TiHKAL the Continuation. Transform Press, 1997. ISBN 0-9630096-9-9