Art. XLVII.—On the Botany of the Pirongia Mountain.
[Read before the Auckland Institute, 30th June, 1879.]
Residents and travellers in the Waikato and Waipa districts are all well acquainted with the picturesque Pirongia Mountain. As Hochstetter well remarks:—“This ancient dilapidated volcano” * * * “with its many peaks and ravines” gives to the Waipa country its characteristic scenery. “The eye never tires of gazing at it, as it always assumes new forms from each new point of view.”
None of our early naturalists appear to have investigated the flora of the mountain. This is the more singular, as it is easily ascended and is in close proximity to the Waipa river,—before the Maori war, a recognized highway into the interior of the country. Dr. Dieffenbach certainly passed over a portion of the mountain in 1841, but it does not appear that he made any collections on the occasion. Dr. Hochstetter, when journeying up the Waipa Valley, in 1859, turned out of his way to climb the much lower and—in every respect—less interesting hill Kakepuku, but made no attempt to ascend Pirongia. Since then the Maori difficulty practically closed the mountain to Europeans until quite recent times. The following remarks are based upon notes made during two ascents, in January 1877 and January 1879, and must be understood as referring to the eastern and central parts of the mountain only, as on both occasions I failed to penetrate to the western side (partly through want of time and the impracticable nature of the vegetation to be passed through after the first summit is reached; and, on the last ascent, partly through opposition raised by the Maoris. At some future time, I hope to examine the remainder of the mountain, and possibly to give a sketch of its entire flora,—to a knowledge of which the present paper is only a slight contribution.
Pirongia is an extinct trachyte cone, standing on the west side of the Waipa river, almost directly opposite the township of Alexandra. Its highest peaks attain an altitude of 2830 feet, but the range of which it is the culminating point maintains for some distance both to the north and south an average height of over 1000 feet. A continuation of the ridge
running northwards forms the Hakarimata mountains opposite to Ngaruawahia, and at its lowest point, near Whatawhata, is crossed by the road leading from the Waipa to Raglan. The southern range ultimately sinks into the limestone plateau, between the Waipa and Mokau rivers and the western coast. From the mountain itself numerous spurs and ridges radiate in all directions, separated by deep and, in many places, precipitous ravines, These are all occupied by mountain-streams, some of them being of considerable size. Those flowing from the eastern and southern sides of the mountain drain into the Waipa; those rising on the north-western flank form the source of the Waitetuna, discharging into Whaingaroa harbour; while all those which spring from the western and south-western sides flow into some of the many inlets of Kawhia harbour. Standing on the top of the peak overlooking Alexandra, the summit of the mountain is seen to be almost split in twain by an immense chasm, over a thousand feet in depth, probably representing an old crater with its outer edge broken down. A similar, but smaller, chasm exists on the southern face of the mountain, and, if Maori report is to be trusted, also on the western side. The separating ridges are in many places little more than sharp-edged walls of solid rock, rising here and there into domes and peaks, and now and then sinking into comparatively low saddles. A peak on the western side is the highest on the mountain, but several of the other summits almost equal it in height.
The whole of the mountain proper is covered with luxuriant forest; but between its base and the Waipa river there exists a narrow strip of open country, low, fern-clad hills, varied here and there with swampy gullies, and supporting a uniform and somewhat scanty vegetation. Pteris, Leptospermum, and Pomaderris are the most abundant plants. Coriaria, Gaultheria, Leucopogon, Epilobium, Haloragis, are all commonly met with; in fact, the facies of the vegetation is precisely that of the tertiary clay hills in the immediate vicinity of Auckland. The swamps contain the usual dense growth of Typha, Cladium, Schænus, and Carex. A rather local species of the latter genus (C. inversa) was noticed in one or two localities. Among naturalized plants Hypericum perforatum was seen in some quantity. It may be remarked, in passing, that this species is spreading rapidly through the Waikato district, and threatens to become a troublesome weed. At Matamata, in the Thames valley, some old pastures have been completely overrun with it.
Entering the forest, the ascent of the mountain is fairly commenced, though for a considerable distance the rise is very gradual. Here our guide pointed out to us the old camping ground—only a few yards distant from the track—where, a few years back, the unfortunate Mr. Todd was murdered by the Maoris while sleeping in his whare. The forest is at first almost
wholly composed of magnificent tawas (Nesodaphne tawa). Nowhere have I seen taller or better-grown specimens, and their cool shade was most acceptable after the hot and dusty tramp over the fern-hills from Alexandra. Mixed up with tawas are scattered rimus (Dacrydium cupressinum), kahikateas (Podocarpus dacrydioides), and ratas (Metrosideros robusta). The last-named tree is much more common on the northern side of the mountain, and on the spurs above Harapipi forms a large proportion of the bush. Dysoxylum, Tetranthera, Knightia and Santalum are all comparatively plentiful. The undergrowth is principally composed of Coprosma lucida and C. grandifolia, Drimys axillaris, Alseuosmia macrophylla, fern trees, and several species of Gahnia and Astelia. Here and there thickets of the climbing Freycinetia banksii are met with, while “supple-jacks” (Rhipogonum), and mange-mange (Lygodium articulatum), are abundant enough. Nor are the climbing species of Metrosideros (M. florida, M. hypericifolia, M. scandens), or the prickly tataramoa (Rubus australis) at all rare.
Little change takes place in the vegetation until an altitude of 1200 feet is reached, when the tawa becomes much less plentiful, its place being gradually taken by Weinmannia racemosa, Quintinia serrata, and Ixerba brexioides. Melicytus lanceolatus was noticed in one or two localities. Here, the first specimens of a new Polypodium (P. novæ-zealandiæ, Baker, ms.) were collected.* It is usually found on rotten logs, rarely growing on the ground, and was not seen climbing trees, like its near allies P. billardieri and P. pustulatum. The rhizome, so conspicuous from its shaggy coating of chestnut-brown scales, is often as thick as the thumb, while fronds were measured (including the stipes) nearly five feet in height, with upwards of twenty pairs of pinnæ. It is abundant over the whole of the higher portion of the mountain.
Above 1500 feet much of the undergrowth is composed of Coprosma fætidissima, well known to bushmen in the south of the Island from its disgustingly fœtid smell when bruised, or even handled. This is the first record of its occurrence to the north of the East Cape. Possibly Pirongia is its northern limit on the west coast, but on the east it has a more extensive range, as it occurs in profusion on the plateau above the Wairere Falls in the Thames Valley, and, according to Maori authority, is also found on Te Aroha. Two other species of Coprosma are associated with it on Pirongia; but, in the absence of flowers and fruit, they cannot be safely identified. One is a small, densely branched shrub, 2–5 feet high, with oblong or obovate leaves 1 inch in length, and may perhaps be a large form of C. colensoi. The other is a tall, slender shrub, with much of the habit of C. grandifolia, but with smaller, narrower, more acuminate leaves, very
[Footnote] * See Trans. N.Z. Inst., X., p. 356.
finely reticulate beneath. This may prove to be C. acutifolia, or a close ally. Panax is a genus well represented on Pirongia. Besides P. arboreum and P. crassifolium, which are found all over the mountain, P. edgerleyi occurs in abundance on the higher slopes. In foliage it is one of the handsomest of the New Zealand species, and should be much more frequently seen in cultivation than it is at present. P. sinclairii is also of frequent occurrence. It had not been previously noticed to the north of Lake Taupo, the habitat of “Auckland,” given in the “Handbook,” being clearly erroneous. P. colensoi is not so common as either of the above, and is seldom seen far from the higher peaks.
Ferns are principally confined to the deep gullies, where they occur in luxuriant profusion. In rocky places, the banks of the streams are fringed for long distances with Lomavia elongata. Dark and gloomy places form the favourite habitat for Lomaria nigra, while in drier and more open localities Lomaria vulcanica is occasionally seen. Trichomanes strictum is abundant; while overhanging trees are loaded with the various species of Hymenophyllum. On dry rocky banks Polypodium australe is more abundant than in any other locality known to me, and attains an unusually large size. It is commonly associated with Lindsaya trichomanoides. Our guide informed us that large patches of the para (Marattia fraxinea) are to be found in the deeper gullies, and that the Maoris often make expeditions to obtain its starchy rhizome. I did not, however, myself observe the plant. In boggy places, near the summit, extensive clumps of Todea superba were noticed: the most northern locality yet recorded for this magnificent species. Dicksonia lanata occurs on some of the slopes near the summit, but nowhere shows any sign of producing an erect caudex, in this respect agreeing with specimens found in similar localities on the Cape Colville Peninsula. It may here be mentioned that Dicksonia antarctica probably occurs on the lower portion of the mountain, as it is plentiful towards the upper part of the Waitetuna Valley, some of the tributaries of which rise on the north-western flank of Pirongia. Several years ago Mr. W. J. Palmer observed it between Lake Waihi and Ngaruawahia, and quite recently the same gentleman has discovered it in abundance to the west of Lake Whangape, at present the most northerly locality known.
Some distance below the summit, the tawa and rata and others of the lowland trees disappear entirely; Ixerba brexioides and Weinmannia racemosa now being the predominant species. Griselinia littoralis and Metrosideros lucida are also plentiful. Rocky places were covered with the creeping Callixene parviflora, a charming little plant with waxy white flowers and berries. Libertia micrantha, which is found over the greater part of the mountain, is here excessively abundant. A few specimens of Chiloglottis
traversii were collected, but all long past flowering. In open mossy places, Hymenophyllum bivalve was by no means rare.
The following plants were seen on the highest of the peaks on the Alexandra side of the mountain, altitude about 2,700 feet:—Rubus australis var. cissoides, Ixerba brexioides, Quintinia serrata, Weinmannia sylvicola, W. racémosa, Fuchsia excorticata, Epilobium pubens, Panax colensoi, P. sinclairii, Griselinia littoralis, Alseuosmia macrophylla, Coprosma lucida, C. grandifolia, C. sp., G. fœtidissima, Gaultheria antipoda, Leucopogon fasciculatus, Dracophyllum traversii, Myrsine salicina, Podocarpus totara (much dwarfed), Callixene parviflora, Libertia micrantha, Cordyline banksii, Cordyline “hookeri,” Phormium colensoi, Astelia trinervia, A. sp. (a small species with very narrow leaves and few-flowered panicles, immature fruit alone seen), Gahnia hectori, Hymenophyllum bivalve, H. polyanthos, H. demissum, Pteris incisa, Lomaria procera. var. minor, Lomaria vulcanica, Polypodium australe, Tmesipteris forsteri. One of the most interesting of the above is Cordyline “hookeri,” the toii of the Maoris, which, on several of the higher peaks, forms small groves of from thirty to forty individuals, usually from 6–10 feet in height. Its broad massive foliage and striking habit of growth render it very ornamental. None of the specimens seen were branched, and no signs of flowers or fruit were observed. Two naturalized plants were collected on the extreme point of the peak, Hypochœris radicata and Rumex obtusifolius, seeds having in all probability been accidentally brought by the surveyors, who have cleared away the native vegetation in order to obtain an unobstructed view in all directions.
The view at sunrise is a most extensive one. The whole of the western coast, from the Manukau Heads to Raglan, was plainly visible. Kawhia Harbour was shut out by the western side of the mountains; but the sea again appeared between Albatros Point and Cape Teringa. Beyond this were the Tapirimoko Ranges and the mountains on the further side of the Mokau River. Over the latter the cone of Mount Egmont stood out clear and sharp against the sky, although over 100 miles distant. Looking eastward, the Waikato plain was stretched out at the very foot of the mountain. Behind it, the view was bounded by the Maungatautari mountain and the Patetere plateau. Southwards, looking over the top of Kakepuku, were the Rangitoto Ranges and the broken and mountainous Tuhua country. And, looking over these again, the lofty snow-clad mass of Ruapehu was easily discernible, the upper part of the cone of Tongariro appearing not far from its side. Lake Taupo was hidden by the mountains surrounding it, but portions of the Kaimanawa Range on the eastern or further side of the lake were clearly visible. Northwards, the view extended down the Thames and Piako Valleys, and was finally closed by the Te Aroha Range and the mountains behind Shortland and Grahamstown.
After exploring the three peaks overlooking Alexandra, a start was made to reach the highest peak by proceeding along the crest of the circuitous ridge separating the crater-like chasms before-mentioned; but the vegetation proved so excessively dense and difficult to penetrate, that after spending the greater part of a day in advancing a distance certainly not exceeding a mile, the attempt was abandoned. Trees dwarfed to the height of a few feet occupied the whole breadth of the ridge, their branches spreading horizontally just above the ground. In some places progress could only be made by creeping on all-fours under the vegetation; in others even this course could not be followed, and the only means of advance was by walking on the tops of the trees themselves, the branches being so closely interlaced and matted together as to bear the weight of a man for considerable distances. This mode of progression, although allowing the explorer the benefit of a good view in all directions, is not without its disadvantages, as it is not always possible to feel certain of the exact height above the ground he is travelling at, and, on reaching a weak place, he usually descends to terra firma much more suddenly than is at all pleasant or convenient. The dwarfed state of the vegetation is evidently more caused by exposure to the strong winds that periodically sweep over the top of the mountain than to the decreased temperature due to altitude; for in sheltered places only a few yards below the level of the ridge the same species could be seen growing luxuriantly. In very exposed places it was curious to see comparatively large trees growing out horizontally from the edge of the leeward side of the ridge, their branches cut off level with its surface as regularly as if trimmed with a gardener's shears. The character of the vegetation differed in no respect from that of the peak before described, being principally composed of Ixerba brexioides and Weinmannia racemosa. The excessive abundance of the former species all over the higher portions of the mountain is a most noteworthy peculiarity.
Although the flora of Pirongia is certainly a luxuriant one, and might be considered a favourable example of our forest vegetation, yet it is by no means so numerous in species as that of districts situated more to the north. In short, an examination of it clearly bears out the conclusion arrived at by several observers that the ligneous vegetation of New Zealand steadily decreases in the number of species as we proceed southwards. Anyone acquainted with the vegetation of the Cape Colville peninsula, or of the hilly district behind Whangarei and the Bay of Islands, or of the range of mountains between Mongonui and Hokianga, and comparing either of them with that of Pirongia, would not fail to recognize this. The number of northern species absent is not counterbalanced by the few southern plants added.
In describing the flora of any district it is quite as essential to point out the absence of any species of general distribution which might have been fairly expected to occur, as to record the presence of rare or local ones. It is true that to assert positively that a particular plant is absent from a locality is a somewhat hazardous statement, and one that should never be made unless founded on a careful and minute exploration—which demands time and leisure. At present, too little is known of Pirongia to make any statements of this kind, but it certainly seems desirable to draw attention to a few plants that were not observed by myself, in the hope that future explorers will do something towards ascertaining whether they are really absent from the mountains or not.
Only two species of Pittosporum were noticed,—P. tenuifolium and P. cornifolium; but surely P. eugenioides will be found near the base, and P. kirki near the summit (the first species being common elsewhere in the Waikato, and the last known to occur in at least one locality). Elœcarpus hookerianus and Pennantia corymbosa are both trees that would naturally be looked for, but neither was observed. No true myrtle was collected, although M. bullata, at least, will doubtless be found. Corokia buddleoides, so common in hilly and wooded districts near Auckland, was not seen. Some of the southern Olearias, as O. nitida and O. dentata, might have been expected. No species of Celmisia was noticed upon the mountain itself, although C. longifolia is found on the bare hills between Harapipi and Whatawhata. Gaultheria rupestris should be found on some of the rocky peaks. All the olives were absent, and only one species of Veronica and one of Pimelea were noticed. I did not observe any of the Fagi, but there seems to be no reason why F. fusca should not occur. A most remarkable peculiarity is the apparent absence of all the mountain species of Dacrydium and of Phyllocladus trichomanoides. Among ferns, Hypolepis distans, Lomaria alpina, and Aspidium aculeatum, are species which may be expected to occur on Pirongia, but which were not observed by me.
Before concluding this paper, it seems not out of place to say a few words about Karioi mountain (situated on the coast, between Raglan and Aotea, and about thirty miles distant in a straight line from Pirongia). So far as can be judged from a single day's examination, its vegetation very closely resembles that of Pirongia; in fact, when a few coast plants—as Vitex, Myoporum, Olearia albida, etc.—are excepted, the plants of the two localites are almost identical. All the southern species seen on the summits of Pirongia—as Coprosma fœtidissima, Panax sinclairii and P. colensoi, Cordyline hookeri, Polypodium novœ-zealandiœ, etc.—re-appeared on the top of Karioi. One marked difference, however, was noticed: Ixerba brexioides, which is probably the commonest tree on the higher parts of Pirongia, is decidedly scarce on Karioi.