Forest Vines to Snow Tussocks: The Story of New Zealand Plants
The New Zealand hook climbers are all species of Rubus, a genus which includes the familiar blackberry and raspberry and is widespread in page 63temperate regions and the montane tropics. In north temperate regions, the species of Rubus do not climb and are shrubs or scramblers in open habitats, but most of the New Zealand species and a number of Australian and tropical species are low to high climbing forest lianes. The adult leaves of most species are palmately compound with three or more leaflets. Backwardly curving hooks or prickles stud the underside of the petioles and leaflet midribs and sometimes the stem as well — a feature which effectively prevents the stems slipping back from any position attained. In colonial times, this tenacity earned for the New Zealand plant the name of 'bush lawyer', a perhaps unwarranted slur on the legal profession of the day. In fact the 'lawyers' are the only plants in New Zealand forests which are prickly. This is in contrast to the rain forests of Queensland and south-east Asia where many spiny climbers are unpleasantly in evidence. The original lack of browsing mammals in New Zealand is the probable explanation for this, and the same would apply for the lack of spiny plants in New Caledonian forests.
The bush lawyers are sometimes included in the 'scrambler' category of vines. Scramblers are small, unspecialised climbers whose weak, drawn out stems grow up between the branches of shrubs and trail over them. The lawyers begin their ascent in a similar way, but their hooks enable them to reach great heights, equal to those attained by more specialised vines.- For this reason I think they warrant a special category. The liane species of New Zealand Rubus occur throughout the country, including Stewart Island, in lowland to montane forest.
The first leaves of the young plants are simple; their stems are quite stout and so are able to stand erect without support for 60 cm or more. If nothing is available to climb, the young plant bends to the ground, branches and spreads widely over the forest floor until some of the branches find supports and make their way into the forest canopy via shrubs and smaller trees. The woody stems, which can be looped on the forest floor as well as extending to the forest roof, frequently produce 'searcher shoots' (Fig. 36). The searcher shoots which are near to the ground can stand without support for one metre or more, and are thus very effective in expanding sites of Rubus foliage in the canopy and in establishing new sites.
The commonest species is Rubus cissoides which has long, narrow and sharply toothed leaflets. The adult stems may be up to 17 cm in diameter and the foliage can reach to 15 m or more above the ground.page 64
Rubus schmidelioides has stems up to 10 cm in diameter, and generally smaller, similarly shaped leaflets, but these leaflets are bluntly toothed and have a dense covering of whitish hairs beneath.
Rubus australis is most common in swamp forest and is sometimes referred to as 'swamp lawyer'. Its leaflets are short, fairly broad and sometimes almost circular. In this species there is a distinct juvenile form, which spreads and roots widely over the forest floor, bearing leaves with small, membranous, more or less round leaflets with reddish coloured veins. At the adult stage this species can reach for 10 m or more into tree crowns, with stems several centimetres in diameter.
Rubus squarrosus is perhaps the most remarkable of the genus, as, in open situations and on shrubs, the leaflet blades remain undeveloped and the leaves consist of rather elongated petioles and the almost threadlike midribs of the leaflets, all beset with yellow prickles (Fig. 37). Such leaves are very effective in clinging to any support. When the stems reach into tree crowns there is a trend towards normal leaves with well formed narrow leaflets. This species is similar in eventual height and stem size to R. australis.