Development of Ideas.—As ideas advanced, the spirits asso ciated with trees were represented by posts, idols, or masks ; altars were added, and the trunk was roughly shaped to represent the superhuman occupant. There is reason to believe that the last mentioned transformation has frequently happened in the devel opment of iconography. Indeed, the natives of the Antilles sup pose that certain trees instructed sorcerers to shape their trunks into idols, and to instal them in temple-huts where they could be worshipped and could inspire their priests with oracles. When the tree-spirit was conceived to be of human shape the numerous stories which associate trees with men or deities of flesh and blood would easily arise; and just as Indian natives have gods which are supposed to dwell in trees, so in higher religions we find a Zeus or a Dionysus Endendros, gods, "occupants of trees," who have been identified with one or other of the leading members of a recognized pantheon. Syrian writers speak of a "king of the forest" and of a tall olive tree to the worship of which Satan seduced the people. But these "trees of the demons" were hewn down by zealous Syrian Christians. So also the caliph Omar cut down the tree at Hodaibaya visited by pilgrims, lest it should be worshipped, and the Council of Nantes (A.D. 895) expressly en joined the destruction of trees which were consecrated to demons.
Tradition has preserved some recollections of the overthrow of tree-cult in Europe. Bonifacius destroyed the great oak of Jupiter at Geismar in Hesse, and built of the wood a chapel to St. Peter. (A similar continuity was maintained near Hebron when Con stantine destroyed the idols and altars beneath the oak or terebinth of Abraham at Mamre and replaced them by a basilica.) On the Heinzenberg near Zell the Chapel of Our Lady stands where the old tree uttered its complaint as the woodman cut it down; and at Kildare (cilldara, church of the oak), "Saint" Brigit or Bridget built her church under an oak tree. On the other hand, at Samosata, the sacred tree worshipped in Christian times was honoured as the wood of Christ's cross, and this growth of a new tradition to justify or at least to modify an old survival recurs in Palestine where the holy trees, whether adjoining a venerated tomb or not, are often connected with the names of saints or prophets and sometimes with appropriate traditions.
monest instance of this; higher and thicker trunks are, however, occasionally presented by the royal fern (Osmunda regalis), in which a height of 2 ft. may be attained, and this with very con siderable apparent thickness, due, however, to the origin and descent of a new series of adventitious roots from the bases of each annual set of fronds. Some tropical members and allies of these genera become more distinctly tree-like, e.g., Todea. Ole andra is branched and shrub-like, while Angiopteris and Marattia may also rise to 2 f t. or more. But the tree-ferns proper are practically included within the family Cyatheaceae. This includes seven genera (Cyathea, Alsophila, Hemitelia, Dicksonia, Thyrs oPteris, Cibotium and Balantium) and about 36o species, of which a few are herbaceous, but the majority arboreal and palm-like, reaching frequently a height of 5o ft. or more, Alsophila excelsa of Norfolk island having sometimes measured 6o to 8o ft. The fronds are rarely simple or simply pinnate, but usually tripinnate or decompound, and may attain a length of 20 ft., thus forming a splendid crown of foliage.
The genera are of wide geographical range, mostly within the tropics; but South Australia, New Zealand, and the southern Pacific islands all possess their tree-ferns. In Tasmania Alsophila australis has been found up to the snow-level, and in the humid and mountainous regions of the tropics tree-ferns are also found to range up to a considerable altitude. The fronds may either con tribute to the apparent thickness of the stem by leaving more or less of their bases, which become hardened and persistent, or they may be articulated to the stem and fall off, leaving character istic scars in spiral series upon the stem. The stem is frequently much increased in apparent thickness by the downgrowth of aerial roots, forming a black coating several inches or even a foot in thickness, but its essential structure differs little in principle from that familiar in the rhizome of the common bracken (Pteris).
Tree-ferns are cultivated for their beauty alone ; a few, however, are of some economic applications, chiefly as sources of starch. Thus the beautiful Alsophila excelsa of Norfolk island is said to be threatened with extinction for the sake of its sago-like pith. Cyathea medullaris also furnishes a kind of sago to the natives of New Zealand, Queensland and the Pacific islands. The long silky or rather woolly hairs, so abundant on the stem and frond leaves in the various species of Cibotium have not only been used as a styptic, but in the Sandwich islands furnish wool for stuffing mattresses and cushions.