Explore England's older parish churches and you may come across the image of a mysterious face formed of leaves, or perhaps disgorging vegetation from the mouth.

Sculpted in stone or carved in wood, the enigmatic figure is known today as the Green Man. It is a term coined by Lady Raglan in 1939, in an article she published in Folklore. Before then, few people took any notice of the curious motif. If guide books or commentators referred to it by name it was the prosaic foliate head'.

Fascinated by an example she saw at a church in Monmouthshire, however, Lady Raglan named it the Green Man and decided that it was the central figure in the May Day celebrations throughout Northern and Central Europe' - essentially the same as the Jack in the Green, Robin Hood, the May King and others. For some years afterwards, the Green Man was widely interpreted as a figure uniting a wealth of traditions in one ancient, pagan spirit of nature.

Since Lady Raglan's time, experts have cast doubt on her wider generalisations. But if her scholarship was open to criticism, there is no question that she proved a publicist of genius. Before long, people were spotting Green Men in extraordinary numbers. And the quest for their meaning began.

As part of the Faces of Oxfordshire initiative in this year's Oxfordshire 2007 celebrations, The Oxford Times will be exploring the Green Man images that can be seen around the county. And our own quest inevitably begins with Oxfordshire's churches.

The earliest representations of the Green Man are almost always found at sites of worship, whether churches, cathedrals or university colleges (which, with their chapels and cloisters, had originally the character of religious foundations). The implication is that the Green Man was not just a decorative motif, but had some religious or magical significance.

Was he truly pagan in origin? The answer is a partial yes, for some faces ingeniously formed of leaves can be seen in Roman temple architecture. The woodland deities of Celtic and Scandinavian religion may also have contributed to the genesis of the figure who certainly has no obvious prototype in the Bible.

Mediaeval stone masons often included non-Christian imagery in church architecture - there was nothing unusual in that. In establishing Christianity in the British Isles, missionaries shrewdly decided not to try and annihilate existing traditions but rather to incorporate them where possible.

So, the heathenish dragons and devils thought to inhabit sacred sites were appropriated to make gargoyles - pointing outwards to protect the church instead of running rampant within.

The superb Norman Church of St Mary at Iffley in Oxfordshire teems with sculpted images. Its amazing south door (pictured) is studded with figures of fantasy and myth, very few of them specifically Christian - centaurs, a merman, a sphinx, dragon-like creatures biting their tails and, very conspicuously, a Green Man, disgorging foliage. Carved around AD 1170, he has a cat-like face often seen in Norman work.

Around the west door more cat masks disgorge beaded bands or ribbons from their mouths, and they interlink to embrace a further wealth of symbolic figures. These curious, disgorging, cat faces may hold clues to the origins of the Green Man and will be discussed in a future article.

Mediaeval representations of the Green Man in Oxfordshire are extraordinarily varied in character. Chadlington's 13th-century Church of St Nicholas has a face whose nose forms a tree trunk with branches sprouting to make the eyebrows.

He is situated on one exterior corner of the east wall, whilst the other corner has a second bearded head, this one apparently sleeping. Might this be a symbolic representation of the same head, slumbering in winter, and bursting into green life in spring?

Lying under White Horse Hill and the ancient Ridgeway path, Woolstone's venerable Church of All Saints has a wood-carved Green Man looking down from a roof boss in the chancel. The timbers are thought to be 15th-century work, and this figure is weeping foliage from the corners of his eyes.

A more classic representation of the Green Man, disgorging greenery from the mouth, can be seen at Dorchester Abbey. The 14th-century head appears on a south east corner interior stone corbel. A rather anguished figure, he dates from the same time as the beautiful Jesse Window whose undulating branches, sculpted with foliage, depict Christ's descent from the Tree.

On the Green Man Trail we have been inviting readers to submit examples they have found around Oxfordshire, and thanks are due to Heather Horner from the Oxford Preservation Trust for directing our attention to the Church of St James the Great at South Leigh. The church is remarkable for its 14th and 15th-century wall paintings; less well remarked is the Green Man carved outside, over the west door. Like the Dorchester figure he appears distressed - on this occasion, practically wailing foliage.

By the later Middle Ages, the Green Man as a human face streaming vegetation had become very widespread in churches. And the figure may have been more influenced by Christian tradition than generally supposed. A book called The Golden Legend compiled by the Italian churchman, Jacobus de Voragine, was among the most popular religious works of the time, comprising a collection of legendary lives of the saints. Compiled around 1260, it survives in some 900 manuscripts and from 1470 to 1530 it was reputedly most often printed book in Europe.

Among many tales, the book describes how Adam, dying at the age of 930 years, sent his son Seth into Paradise to fetch seeds from the tree of mercy. When Adam died Seth placed the kernels under his father's tongue - and out of his mouth grew trees which yielded the wood of the Holy Cross on which Christ suffered his passion.

Is it possible that this specifically Christian story was in the minds of some, at least, of the mediaeval craftsmen as they fashioned their haunting images? Certainly, a sense of human relatedness to green nature is not alien to Biblical tradition. Isaiah 40 contains the famous quotation All flesh is grass, and all the goodliness thereof is as the flower of the field The grass withereth, the flower fadeth'. The idea that man and nature are one - that we come from the earth and must one day return to it - is also voiced in the quotation from the Book of Common Prayer often spoken in prayer at funerals: Ashes to ashes, dust to dust'. The concept of viriditas, the greening of the soul' by the sacred life force of God's spirit was key to the visionary thinking of 12th-century Benedictine, Hildegarde of Bingen. For this remarkable mystic, composer and herbalist, Springtime is filled with viriditas, and God breathed viriditas into Adam and Eve in the Garden to give them life.

To write (as even some church guides do) that the Green Man is a pagan fertility symbol' does not truly do justice to the complexity of the different strands woven into his evolution. It may be that in looking at the Green Man in his many imaginative incarnations we may be examining at least two different characters. One is a leaf mask, often rather mischievous, with likely origins in pagan nature spirits. The other is a recognisably human head streaming foliage from mouth, eyes or nostrils. Whether influenced by the legend of Adam or not, he seems to have a more primal grandeur - he is generating green life - and may be anguished, grotesque or serene depending on how the craftsman interpreted his theme.

The Green Man Trail is an ongoing initiative, and if you have any information do get in touch. Visit www.greenmantrail.co.uk for information and updates.

To contact us email info@greenmantrail.co.uk For more on Oxfordshire 2007 visit www.oxfordinspires.org/specialevents2007 Secrets of the Misericords Oxford's New College, founded in 1379 by William of Wykeham, Bishop of Winchester, is a place of immense allure for the Green Man enthusiast. Foliate masks adorn the Holywell Street front; others can be seen looking down from the roof bosses in the entrance porches; another still, radiating a sunburst of vegetation, adorns a boss at the approach to the Chapel. But the supreme treasures are found among the wood-carvings in the Chapel itself. The 14th-century misericords present a magnificent array of scenes. There are 62 in all, and they include several Green Men.

The word misericord comes from the Latin word misericordia, meaning compassion. And it was applied to a shelf under a choir stall seat which offered merciful relief to church-goers in the Middle Ages. Tipping up the seat allowed a person to perch on the shelf and take the weight off their feet - while looking as if they were standing. This must have been a boon to the elderly and infirm attending the very long mediaeval church services. Green Man figures can often be found on misericords which evidently furnished wood-carvers with semi-hidden sites on which to indulge their creative flights of fancy. Here they displayed many droll scenes of daily life, as well as creatures from the shadowy realms of the mediaeval psyche. On New College's Chapel's misericord 20, two wickedly grinning leaf masks chuckle to either side of a scaly monster; others Green Men here are faces with leaves issuing from eyes (misericord 6), mouth (misericord 26) or nose (misericord 34).

The Green Man is a recurrent motif in New College's hall panelling, too. By no means all of the building's figures are as old as those in the Chapel, but that only adds dimension to the Green Man mystery. Craftsmen who worked here evidently kept the tradition alive over centuries. Were they obeying some formal instruction, or responding intuitively to the Green Man's meaning? Perhaps we shall never know.