Art. LVIII.—Description of a new Species of Isoëtes.—
[Read before the Wellington Philosophical Society, 29th August, 1874.]
The genus Isoëtes has been added to the New Zealand flora since the publication of the Handbook, the first species having been discovered in the Waikato Lakes by Captain F. W. Hutton and myself in 1869. The plant which forms the subject of the present notice was discovered by Captain Hutton and Mr. W. T. L. Travers three years later in Lake Guyon, Nelson, at an altitude of 3,000 feet. I am indebted to Mr. Travers for specimens.
Not having the opportunity of referring to the recently described austral species of this genus, I can only venture to offer a brief diagnosis under the provisional name of I. alpinus, and indicate its chief points of difference from the lowland species, I. kirkii, Braun.
Isoëtes alpinus, n.s.
Fronds numerous, ten to fifty or more, stout, rigid 4” — 6” long; phyllopodes extremely dilated, with the border produced for some distance along the edge of the frond; sporangium broadly elliptic, 4-septate; ligule minute, triangular; macrospores globose, perfectly smooth, except the faint tricrural line; microspores ovate, closely tuberculated, faintly angled, longitudinal furrow obscure.
Hab.—Lake Guyon, Nelson, alt. 3,000 feet—Messrs. Hutton and Travers; Lake Pearson, Canterbury, if I am correct in identifying a very imperfect specimen collected by Dr. Berggren with the present plant.
Solitary specimens of Isoëtes alpinus often exhibit from sixty to seventy crowded fronds, radiating in a circle of from six to seven inches diameter. The central vascular portion of the frond is also largely developed.
Our plant is readily distinguished from I. kirkii by its robust habit and larger size: and especially by the smooth macrospores and tuberculated microspores.
Plate XXV.—Isoëtes alpinus, nat. size.—Fig. 5, Phyllopodium containing macrospores. 6, Sporangium. 7, Transverse section of ditto. 8, Macrospores. 9, Microspores.