As stated in the previous post, bark is a mixture of living and dead cells.  Cork cells abound, especially in trees like the cork oak, where the cork may be regularly harvested.  This may be used for flooring, insulation and yes - corks for wine bottles. However, bark is a source of many things.  From early times, bark from trees like alder, buckthorn, oak, birch etc were used to make dyes for clothing.  Material from the inner bark of some trees (e.g. lime, willow, mulberry) was a source of fibres for clothing and cordage (string / yarn). Herbalists also found a use for the bark of certain trees.  Infusions of willow were used to treat fevers, the ‘ague’, rheumatic aches and pain.  It contains salicin, which the body converts to salicylic acid, an early 'form' of 'aspirin'. Interestingly, Nicholas Culpeper, in The Complete Herbal (of 1653) gives a number of uses for willow, including to staunch wounds, but does not mention pain control. The bark of the Cinchona [Jesuit’s bark] gave quinine - a treatment for malaria [caption id="attachment_39935" align="alignleft" width="300"] Amber[/caption] When a tree, like a pine, is injured (through storm damage or insect attack), the bark can produce resin - a sticky and viscous liquid.   The resin is produced in resin ducts present within the bark tissue, though the ducts may be present in deeper tissues. Research has shown that ponderosa pine trees that had more (and wider) resin ducts survived drought and bark beetle attack better.  The resin can harden and help seal wounds . Many resins contain terpenes, such as alpha-pinene and limoneme.  The resin from pine and other conifers can under special circumstances be converted into amber.  Sometimes, the resins produced can be fragrant. Trees of the genus Boswellia and Commiphora produce a aromatic resin that gives frankincense and myrrh respectively.  Both are produced by the wounding of a tree so that its resin seeps out.  Both may be used in the making of incense. Another bark exudate comes from certain species of Acacia - Gum arabic, which forms from the hardened sap (adjacent image).  Acacia species belong to the ‘Bean’ family (Fabaceae).  The gum is collected from trees, mostly in Sudan and the Sahel.  Gum arabic is a mixture of glycoproteins and polysaccharides.  The polysaccharides are constructed from the sugars arabinose and galactose. It is soluble in water and edible, and has a number of uses in the food and pharmaceutical industries. Tapping or wounding the bark of different trees can result in various fluids being released, for example, latex.    White or yellow latex is produced by the rubber tree (Hevea brasiliensis).  The latex is found in special vessels within the bark - laticifers. The process of tapping rubber trees is outlined in some detail here.   Latex production is not confined to woody trees, small herbaceous plants like dandelion and spurge can produce a white, milky latex (as can the opium poppy). [caption id="attachment_39984" align="alignleft" width="300"] Euphorbia latex[/caption] The latex produced by some members of the Spurge family can cause burning pain, inflammation or even blistering - for example that of the Pencil tree.  Such toxic saps most likely evolved to deter animals from grazing. Sometimes, a watery sap may be collected from the bark.  This is the case with Birch.  Sap may be collected (tapped) in early Spring, when sugars and other materials are being mobilised for growth, leaf production etc.  Sap may be collected later but is said to then have a bitter taste.  The sap is an interesting ‘cocktail’ of amino acids, protein, sugars (glucose & fructose), betulinic acid, proteins, vitamins C & B, and minerals.  It is used to make a much favoured drink in Northern Europe and should be consumed within days of collection.  Birch trees are quite sensitive to tapping. Not watery, but very sugary is Maple Syrup. Maple trees are tapped by drilling holes through their bark and into their trunks. Starch is stored in the trunks and roots before winter, it is then converted and mobilised in late winter / early Spring. The collected  sap (through tapping) is then heated to produce a concentrated syrup. Thanks to Montemari at Pixabay for image of gum arabic

According to some interpretations of the bible, the Magi or ‘wise men’ travelled from afar bearing gifts of gold, frankincense and myrrh to present to the infant Jesus. The meaning and significance of these gifts has been debated over the years.  One things is clear - all were valuable materials as might have been presented to a king or deity.  Together with spices, frankincense and myrrh moved through ancient trade routes for thousands of years. Gold is a relatively rare element and as such is a precious metal that has been used for jewellery and coinage throughout recorded history.  It is a noble metal, that is it is relatively unreactive, resisting attack by most acids - with the exception of aqua regia, a mixture of nitric and hydrochloric acids. But what of frankincense and myrrh?   Their origins are not geological as both are plant products.  They come from a group of plants known as the Torchwood family or the Burseraceae.  These are trees or shrubs that have prominent resin ducts / canals.  The resin ducts are tubes, surrounded by cells which produce and secrete a resin into the canals / ducts.  The resin is viscous, ’antiseptic’ and aromatic (often smelling of almonds) and helps to prevents microbial attack (and may deter wood boring insects). Frankincense comes from trees of the genus Boswellia.  Nearly all species of this genus have a bark that produces an aromatic sap but it is B. sacra, (also known as the olibanum tree) that is the main source of frankincense (from its papery, peeling bark).  It is found in Somalia, Yemen and Oman, often growing in relatively inhospitable places.  To obtain the resin, the bark of the tree is cut and resin seeps out and is collected, rather like the tapping of a rubber tree.  The trees do not produce resin until they have reached a certain maturity and over-exploitation of the trees can lead to their death.  The seeds from heavily tapped trees are less likely to germinate than those from trees that have not been ‘drained’ of resin.  All Boswellia species are threatened by habitat loss, over-exploitation, and damage by long horn beetles. What is Frankincense used for?  The word derives from the Old French ‘franc encens’ meaning high quality incense.  Many tonnes of frankincense are traded each year and are used in religious ceremonies, and in the making of perfumes and natural medicines.  In ancient times, the Egyptians used it in the process of mummification, it was added to the body cavities together with natron (a mixture of sodium salts).  The resin has also been used in traditional Chinese medicine for its antibacterial properties and ‘blood moving’ properties. Like Frankincense, myrrh is a resin harvested by wounding the bark of a tree. The bark is a silvery grey, and the twigs are quite spiny (see image).  The resin that exudes is ‘waxy’ and quickly congeals becoming hard and glossy, darkening as it ages. The tree in question is Commiphora myrrha.  It is found in north east Africa - Somalia, Yemen, Eritrea and parts of Saudi Arabia.   The related Commiphora gileadensis, native to Israel, Palestine and Jordan, is also accepted as an alternate source of myrrh.  Myrrh has been used as an antiseptic in mouthwashes, and as a constituent in salve / ointment for skin abrasions, bruises and sprains.  It  has also been used in perfumes and  as a special flavouring for wine.  Like frankincense, it was used in making incense❋ and in the preparation of bodies for mummification / embalming.  In Exodus [30:22-24], God said to Moses to take the best spices and liquid myrrh to make a holy anointing oil.  Anointing oil is still used in certain ceremonies / rituals of both Eastern Orthodox and Western Churches.  In some cultures, it can be used to ‘fumigate’ or refresh a house, giving a warm, earthy and balsamic odour.  It is also said that myrrh is a powerful detoxifier, can lower cholesterol and stabilise blood sugar levels.  Both frankincense and myrrh were extensively traded in ancient and more recent historic times, along with various spices (such as cinnamon, ginger and nutmeg) across the Mediterranean and Arabian peninsula, through to India.  Interestingly, in Ancient Rome, myrrh was priced at five times the cost of frankincense. ❋ Incense can be made from various aromatic plant materials that produce a scent. The actual ingredients used vary by region / area. Apart from frankincense and myrrh, incense may contain cinnamon musk patchouli (from a plant of the mint family) sandalwood. Many thanks to Pixabay for images of frankincense and myrrh  (Leo_65, xbqs42  et al))   .