Art. XLIV.—Notice of a remarkable Arborescent Fern on Ngongotaha.
[Read before the Auckland Institute, 14th October, 1872.]
At the height of about 1,400 feet on Ngongotaha, a wooded peak on the south-west side of Rotorua, I met with a remarkable specimen of Cyathea dealbata, Swartz, the silver tree-fern of the settlers.
The specimen is between nine and ten feet in height, with the trunk somewhat inclined; at about eight feet from the ground it divides into two branches, each under eighteen inches in length; one of these is again divided, but the branches have not diverged, and are growing in such close contact as to resemble at first sight rather a single branch with a double crown, than two distinct branches. All the branches are crowned with fronds.
The trunk presents no marked feature, but the branches are much thickened and swollen, partly from being covered with a dense coat of hardened paleaceous scales; amongst these scales lateral crowns have become developed and given off fronds, varying in number from three to five on each, crown, and from six to fifteen inches in length.
This singular specimen had evidently been recently scorched by fire, which had destroyed a portion of the old fronds; new fronds were developing in the greatest health and vigour.
From the condition of the branches, I am led to infer that they owe their origin to a division of the growing point arising from the attacks of insects, and that a continuance of the same cause has led to a development of the lateral crowns. This might possibly have been proved or disproved by a
dissection of the branches, but as the destruction of the specimen, which is probably unique, would have been involved the idea was not entertained.
The whole process is strictly analogous to that which takes place under similar circumstances in phænogamic plants, although the formation of lateral crowns in plants which do not produce buds cannot be satisfactorily explained at present.
A similar case is recorded as having occurred in a Javanese Alsophila, but I am not aware of any other instance having attracted notice.
Branched tree-ferns are so extremely rare that they usually attract the attention of settlers in the districts in which they occur, but on the range of hills of which Ngongotaha forms the extremity, I found three specimens of Dicksonia squarrosa, Swartz, each with a single branch, in symmetrical and healthy condition. At Great Omaha I discovered a single branched specimen of Cyathea dealbata, Swartz, the branch about six feet in length; another specimen occurs in the Hunua, and a third is said to grow on the Great Barrier Island. Colenso describes a remarkable specimen of this species, three-branched at five feet from the ground, each branch being four feet in length, growing at Owae.
I am not aware that any branched specimens of C. medullaris have been observed, but in the parish of Opaheki a remarkable specimen of C. cunninghamii is still growing; the main trunk is inclined to about eighteen inches from its base, when three erect branches are given off; the outer being respectively nine and ten feet long; the central one about six. All the branches are crowned with vigorous fronds.