The four main devices (symbols) in the Jack blazon are the oak leaf, acorn, escallop and crescent. The two main tinctures (colors) are vert and sable.
The deep green colour that is so often observed in heraldry is more properly known as vert. According to Wade, the use of this colour signifies “Hope and Joy”, but may also represent, rather delightfully, “Loyalty in Love” 1. It has other names also, the French call it sinople, perhaps after a town in Asia Minor from where the best green die materials could be found 2. More fanciful heralds liked to associate it with the planet venus and the precious stone emerald 3. More strangely, there is some evidence that the term prasin was anciently used, being the Greek for the vegetable we call the Leek!
Sable, the deep black so often found in Heraldry is believed to named from an animal of the marten family know in the middle ages as a Sabellinœ and noted for its very black fur 4. In engravings, when colors cannot be shown it is represented as closely spaced horizontal and vertical lines, and appropriately is thus the darkest form of hatching, as this method is known 5. Although it may seem a sombre tone, and does indeed sometimes denote grief, it is more commonly said to represent Constancy 6.
Amongst the natural objects depicted on a coat of arms, trees feature frequently, either in whole or as individual branches and leaves. 7. Although sometimes described simply as a tree most often the specific species was named, and the oak tree or oak leaf is a typical example that frequently is depicted in arms, sometimes fructed with acorns of a different colour. 8 For good reason, Wade assigns the meaning of “antiquity and strength” to this symbol. 9
Amongst the natural objects depicted on a coat of arms, trees feature frequently, either in whole or as individual branches and leaves or fruit. 10. The acorn, often represented in its early state as vert (green) 11 can be associated of course with the mighty oak, signifying, according to Wade, “antiquity and strength”, for obvious reasons.
The escallopoccurs often in arms, represented as the outside of the shell, sometimes “fluted” of a different colour 12. It has been part of heraldic tradition almost from the beginning of the art, Henry III of England awarded Gules, 3 escallopes argent to Herbert de CHAMBERLEYNE in the 13th century, and it is present in the heraldry of almost all countries 13. It is believed that they were adopted as badges of those going to the Holy Land and can be found in the arms of many a crusading family. Hence Wade’s suggested association of the scallop with those that “complete long journeys to far countries” 14.