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THE TREE FERNS OF NORTH AMERICA.

[With 15 plates.]

By WILLIAM R. MAXON.

Although the name tree fern is occasionally given to any large fern of treelike form, it has come by common usage to have a definite application to the members of a single family, the Cyatheacon, and in so far as any one descriptive term can apply to a large group of world-wide distribution, whose distinctive technical characters are minute and not always very obvious, the expression is a singularly appropriate one. The Cyatheaceae are known as tree ferns because the great majority of the species are essentially treelike in size and proportion and have strong woody trunks, often attaining a height of 40 feet or more.

One may easily imagine the feeling of surprise with which the early voyagers to the New World, looking upon the wonderful profusion and luxuriance of these enormous plants, contrasted them with the relatively small ferns of Europe. One wonders also at the restraint and rather passive scientific attitude of Sloane, one of the earlier English writers upon the West Indian flora, who, having accompanied the Duke of Albemarle upon his voyage to Jamaica in 1689, thus quaintly describes a common species (Alsophila aspera), as he observed it in that island:

This has a trunc twenty Foot high, as big as ones Leg, (after the manner of Palmtrees) undivided, and covered with the remaining ends of the Foot-Stalks, of the Leaves fallen off, which are dark brown, as big as ones Finger, two or three inches long, thick set with short and sharp prickles. At the top of the trunc stand round about five or six Leaves, about six Foot long, having a purple Foot-Stalk, very thick beset with short, sharp prickles on its backside. At about a Foot distance from the Trunc, each Leaf is divided into Branches set opposite to one another, placed near the bottom, at about six Inches distance from each other.

The ultimate divisions (segments) of the leaf are mentioned as about one third of an Inch long, and half as broad, blunt, easily indented about the edges, of a dark green colour above, pale green below, very thin, and so close set to one another that there is no defect or empty space between them.

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From this description, brief as it is, several of the most characteristic features of the group as a whole may be noted: The single and simple unbranched trunk or stem, "after the manner of palm trees, the spreading circular crown of ample fronds surmounting the stem, the lighter color of the under surface of the leaf, which may be observed in nearly all Cyatheaceae, not a few of the species being grayish or even whitish below, and above all the "close-set" divisions, without "defect or empty space between them," a feature which in connection with the enormous size of the fronds of many species. lends to tree ferns their greatest charm, that of surpassing leafiness and vigor.

For the benefit of the ignorant or of the superficially minded Sloane adds:

From these Trees growing on the Mountains of Hispaniola the Spaniards argued the fertility of that Soil, making Ferns grow to such a vast bigness, which in Europe were so inconsiderable, not considering that the Ferns in Europe and here, were quite different kinds one from the other.

Not alone in dimensions, but also in technical characters of structure are the huge ferns of this alliance distinct from those of continental Europe. Sloane calls them "trees," and to this day the term "fern tree" is employed in Australia as commonly as our more familiar "tree fern" for members of the Cyatheaceæ. "Fern-tree gullies" is there a common expression, applied to deep shady ravines of the moister coastal regions having a dense growth of Cyatheaceæ.

ARBORESCENT HABIT.

A typical group of tree ferns of different ages is shown in plate 1, a scene in Guatemala. The species is Cyathea princeps (often known as C. Bourgaei, and described more recently as C. Munchii), a rather uncommon plant which ranges from the moister parts of Mexico to Alta Verapaz, eastern Guatemala. Not all species of Cyathea have their fronds so rigidly ascending. Indeed, Cyathea arborea, which is the commonest and perhaps the most graceful North American member of the genus, will be seen (pl. 2) to have them laxly arching or even drooping. The direction of the fronds, however, in many species depends much upon the age of the plant. Thus, the smaller individual at the right in plate 1 owes the upright position of its fronds in part to its quick, vigorous growth and partly, no doubt, to the need the plant has of stretching its leaves up toward the level of the rather dense surrounding undergrowth, where of course the sunlight is much stronger than below.

Tree ferns may in fact be regarded as "standing on 'standing on tiptoe" in their effort to secure light and air. They are commonest in those moist, densely forested, tropical regions where their struggle for

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