Art. XLVI.—Remarks on Paratrophis heterophylla, Bl.
[Read before the Wellington Philosophical Society, 17th February, 1897.]
Plates XLV. and XLVI.
Most New Zealand botanists have doubtless felt considerable uncertainty as to the specific identity of certain plants included; rightly or wrongly, under Epicarpurus microphyllus, Raoul, the “turepo” of the Maoris and the “milk-tree” of the settlers. Certainly any ordinary observer examining Raoul's beautiful drawing, and comparing it with the fine plate of Trophis opaca in the Banksian collection, would unhesitatingly conclude that two entirely different plants were represented by the artists, and for some time past I have been of the same opinion; but the examination of a large number of specimens from various localities has compelled me to believe that we have only a single species which exhibits an exceptional range of variation, so that it is desirable to point out the characteristics of the extreme forms.
Paratrophis heterophylla, Bl., Mus. Bot. Lugd. Bat., ii., 81.
In the young state the typical form has slender, flexuous, often tortuous twigs with brown bark, pubescent or even setose at the tips, and very brittle; the leaves are distant, membranous, green, ½ in.—¾ in. long, shortly petioled, varying from obovate to obovate-orbicular, cuneate at base, entire or deeply-lobed below, or even pinnatifid, acute, sharply toothed; stipules ovate - subulate, caducous. In this state the plant forms a bush or shrub 3ft.—8ft. high, which bears but a slight resemblance to the mature condition and rarely produces flowers.
Gradually the leaves become coriaceous, the bark changes to a grey colour, sometimes almost white, the leaves become obtuse, or even retuse, their, margins crenate or crenate-dentate, while the location is less prominent and often disappears. The obovate outline may be retained or pass gradually into obovate-elliptic or elliptic-ovate; the length may vary from ½ in. or less to 1 ½ in. In this state the plant may range from a shrub or bush to a small tree 40ft. high or more, with a trunk not exceeding 24in. in diameter, and pale-grey or whitish bark. Flowers are produced freely, the male catkins forming axillary or rarely terminal amenta ¾ in.—1in. long, the flowers mixed with curious peltate scales,
having scarious white : margins. Perianth deeply 4-partite, lobes rounded, ciliate; stamens 4, exserted. Female flowers in short 3—6-flowered spikes; flowers distant; perianth deeply 4-partite, the outer segments smaller than the inner; stigma short, bifid; ovary 1-celled, 1-ovuled. Fruit as large as a peppercorn, 1-seeded, red, spherical, tipped with the short straight style. The slender rhachis becomes pendulous as the fruit ripens; it is remarkable that the fruits are almost invariably solitary, although the spikes are 3—6-flowered.
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Var. elliptica is erect from a very early stage, and does not appear to pass through the remarkable stages of leaf-variation described above. It may be, however, that more extended observation might render it necessary to modify this statement, but I have seen no indication of such change. The twigs are straight, erect, with brown bark. The leaves are erect and rather close set from the first, oblong or elliptic-oblong, acute, subacute, or obtuse, margins crenate or crenate-dentate, coriaceous, 1in.-3 ½ in. long, 1/3 in.—1in. broad, slightly narrowed at both ends, but not obovate. Both male amenta and female spikes are often geminate, although usually solitary, and are larger than those of the type, sometimes 1 ½ in. long or more. The drupes, however, are numerous, the size of small peas, and, being produced in great profusion, resemble at a short distance racemes of red currants, the resemblance being increased by the slender rhachis being invariably pendulous. It seems not unlikely that the greater number of perfect fruits on a spike in this variety may be due to the spikes being usually developed on the naked portions of the branchlets, and thus being more readily fertilised than when hidden amongst the leaves, and it is not impossible that the more robust habit of this plant may be indirectly connected with the same characteristic. Notwithstanding the very different aspect presented by the extreme forms, a gentle gradation may be traced from the small membranous lobulate or pinnatifid leaves of the early stage of the type to the large elliptical entire leaves of var. elliptica, but it is not easy to find intermediate stages among the drupes.
Female flowers appear continuously through the season, especially in var. elliptica, in which they are developed to the end of February. In this form the unfertilised stigmas often remain on the rhachis until the drupes are nearly ripe. The wood is white, compact, and rather hard, but perishable.
Trophis opaca, Banks and Sol., ex Hook. f. Fl. N.Z., i. 224. Epicarpurus microphyllus, Raoul, Ann. Sc. Nat., ser. iii., ii. (1844), 117; Choix de Pl. de la Nouv.-Zél., xiv., t. 9; Hook f., Handbk. N.Z. Fl., 251. Taxotrophis microphylla, F. Muell., Fragm. Phyt. Austr., vi., 193.
Hab. North and South Islands: Mangonui to Foveaux Strait. Great Barrier Island.
Var. elliptica = Trophis opaca, Banks and Sol., MSS. et Ic.
Hab. North Island: Mangonui to Cook Strait. Taranga Islands. Stephen Island. Chiefly in places near the sea.
The Banksian plate exhibits the male and female spikes mostly arranged in threes, springing from a terminal peduncle I have not seen a specimen exhibiting this peculiarity.
It should have been mentioned that the male and female inflorescence is frequently metamorphosed into small but much-branched panicles, the branchlets of which are densely clothed with minute imbricating scales, without any trace of the organs of fertilisation. This diseased condition is most common in the small-leaved forms.
I have to express my indebtedness to the Bishop of Waiapu, to Frank V. J. Williams, Esq., of Waipara, to A. Williams, Esq., of Tuparoa, and other friends, for a copious supply of specimens from various localities; also to the authorities of the British Museum for a precious fragment of the original specimen in the Banksian collection.
The absence of any form of this plant from the Chatham Islands and Stewart Island is remarkable.
Explanation of Plates XLV. and XLVI.
Paratrophis heterophylla, Bl.
1. Leaves of young state.
2. Male flowers.
3. Female flowers.
All natural size.
P. heterophylla, var. elliptica.
1. Mate flowers.
All natural size.