Seventh Meeting: 6th October, 1909.
Present: Mr. Edgar R. Waite (President), in the chair, and fifty others.
New Member.—Mr. R. D. Barker.
Papers.—1. “On the Influence of Ripples on the Gas Content of the Christchurch Artesian Waters,” by Dr. C. Coleridge Farr and D. C. H. Florance, M.Sc.
The experiments described in this paper were undertaken with a view to determining the nature and quantity of the dissolved gases in the water of the artesian wells, in order to decide whether the curious effects found in fish and on their eggs and fry when confined noar outflow of a well could be attributed to the presence of any gas. The principal gases dissolved were found to be nitrogen, oxygen, and carbon-dioxide, and of these nitrogen is in excess of the normal saturation-value, whilst oxygen is in defect. The way in which the saturation-values were reached on rippling over obstacles was examined and compared with the change of effect on fish confined in boxes into which the water was rippled.
2. “Petrological Notes on Rocks from the Kermadec Island, with some Geological Evidence for the Existence of a Subtropical Pacific Continent,” by R. Speight, M.A.
The author gives some account of a collection of rocks from the Kermadec Islands, now in the Canterbury Museum. These are, with one exception, andesites of basic affinity and basalts. Fragments of granite frequently occur on the islands, but the rock has not been found in position. This suggests that the island has been built up on a continental area either a little above sea-level or but slightly submerged. Brief reference is made to the geological evidence for the existence of a former Pacific continent, as demanded by various zoologists in order to explain distribution in the south-west Pacific region. The Kermadecs no doubt formed part of this area, which probably broke up in late Cretaceous or early Tertiary times.
3. “The Vegetation of the Kermadec Islands,” by Reginald B. Oliver.
The paper is descriptive of the plant covering of the Kermadec Islands, and gives a list of the species of pteridophytes and spermaphytes inhabiting the group. It is the result of several months'i nvestigation on Sunday Island by the writer during the year 1908.
The main portion of the paper is devoted to the descriptions of the plant-formations of the Kermadec Islands. These are arranged according to the probable order of their evolution, and fall into five groups.
The coastal formations include rocks, sand-dunes, ngaio scrub, &c. Such characteristic plants as Coprosma petiolata and Scœvola gracilis, together with some New Zealand and some tropical forms (e.g., Ipomœa pes-caprœ, Canaialia obtusifolia) are inhabitants of these situations.
The common bulrush (Typha angustifolia) is the principal swamp-plant. On inland cliffs Poa polyphylla, Asplenium Shuttleworthianum, and a new species of Veronica are usually to be found.
Forest which owes its existence to a humid atmosphere is the principal plant-formation on Sunday Island. It covers the hills from sea-level to their summits, and is only absent from such places as were destroyed by a volcanic eruption in 1870, and a few clearings made by the settlers.
Under the heading “Young Formations” are included those which have grown since the eruption of 1870, and the landslip of 1904. These will ultimately become forest.
“Introduced Formations” are certain meadows where the principal plant is an imported species. There are three described from the Kermadec Islands—buffalograss and Ageratum conyzoides on Sunday, and beard-grass on Macauley Island.
The flora of the Kermadec Islands is most fragmentary, and characteristic of oceanic islands where plants are accidentally carried by ocean-currents and possibly other means. The greater number of species have been received from New Zealand, but Polynesian and Norfolk Island forms constitute the largest part of the vegetation.
The floras of Lord Howe and Norfolk Islands are considered in this connection, with the result that the writer believes them to be remnants of the larger one which migrated from Malaya by this way to New Zealand, together with a number of Australian forms which have arrived from time to time across the intervening space of ocean.
The three groups of islands possess oceanic floras, and properly are included in the New Zealand biological region, and together form a subregion for which is proposed the name “subtropical islands province.”
From the number of kauri logs and pieces of D'U rvillœa and other Algæ cast up on the shores of Sunday Island, it is evident that the strongest and most frequent ocean-currents reaching the group are from the direction of New Zealand, and this, in the writer's opinion, is sufficient to account for the preponderance of New Zealand forms in the flora of the Kermadecs.
4. “On a Non-flowering New Zealand Species of Rubus,” by Dr. L. Cockayne.
A form of Rubus from Westland is dealt with related to R parvus, but differing in its leaves being compound, larger, and somewhat different in colour and serration. The plant has been in cultivation twelve years, grown under many conditions, and yet has never flowered. The author considers that possibly it is incapable of flowering, and that it originated as a non-flowering species, either by mutation from R. parius or as a hybrid between that species and R. australis.
5. “List of Lichens and Bryophytes collected in Stewart Island during the Botanical Survey of 1908,” by Dr. L. Cockayne.
Fifteen lichens, thirty-six liverworts, and thirty-four mosses are enumerated, a reference being given in each case to the “Handbook of the New Zealand Flora,” if the species occurs in that work. The stations of each species are briefly indicated.