Art. XXX.—On a remarkable branching Specimen of Hemitelia smithii.
[Read before the Wellington Philosophical Society, 19th January, 1887.]
Plates XII., XIII.
The visitor to the slopes of Mount Cargill, near Dunedin, may have noticed the marked abundance of that beautiful tree-fern Hemitelia smithii, which often attains there a height of 20–30 feet; and he may also have noticed a strong tendency in this species to divide at the top of the stem into two, and sometimes three, branches. But a remarkable departure, however, from this limited terminal branching has been discovered, which forms the subject of the present paper. The accompanying sketch, drawn from measurements, proves the tree to have been 16 feet in height, and that it has 16 branches, as also several buds. The budding and branching may proceed from any part of the stem, and the specimen has several branches diverging in various directions, which again divide, as in dicotyledonous trees. The accompanying drawings (Plates XII. and XIII.) have been sketched by measurements taken from the fallen tree, it having recently been cut down by some boys.
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The transverse sections are intended to illustrate the method of branching in this specimen of tree-fern; they are all drawn one-third natural size, except diagram A B, which is 1/135 natural size.
There is one remarkable feature in connection with the true or inner stems and branches of tree-ferns: that is, the point of attachment of the branch with the inner or true stem does not increase much in diameter for several inches from the parent stem; it then gradually enlarges in an upward direction, and becomes covered by the fibrous mass. A weakness in branches might be suggested from this; but the great strength of tree-ferns is due to the strong fibrous matter enveloping them, which is remarkably strong, and would prove as reliable for a transverse strain as many timbers; they have often been used for short bridges, both as stringers and flooring.
In the diagrammatic section, A B, is shown the method of branching in this tree-fern: a branch is produced from a small bud, which pushes its way through the woody inner or true stem of the tree, and also the close fibrous outer covering. (See longitudinal section of A 1, where a transverse and longitudinal section is shown of the method of branching.) The large sections (B B and B 3) are cut 3 feet above A, showing the increase of size in 3 feet of the central core.