Included here is the Chatham archipelago situated in the South Pacific some 450 miles east of New Zealand. The largest is Chatham Island measuring about 30 miles in length while the next largest, Pitt Island, barely measures 8 miles. The main forests can be broadly divided into lowland and tableland types.

Chathamian Lowland Forest

With possibly one or two exceptions most of the lowland trees in these forests are evergreen and most of them including Olearia traversii (Asteraceae), Coprosma chathamica (Rubiaceae), Corokia macrocarpa (Argophyllaceae), Hymenanthera chathamica (Violaceae), Mrysine chathamica (Myrsinaceae), Plagianthus chathamicus (Malvaceae), Pseudopanax chathamica (Araliaceae) and Veronica gigantea (Scrophulariaceae) are endemic or near endemic. Also scattered in these forest, often rising well above the canopy, is the endemic palm Rhopalostylis baueri (Arecaceae). On the edges of the forest, especially in some of the wetter areas, the endemic Dracophyllum arborea (Epacridaceae) and Senecio (Brachyglottis) huntii (Asteraceae) can occur in great abundance. Dracophyllum is of interest in that it goes through a broad-leaved juvenile form, which eventually changes into a needle-leaved adult form. This is thought to be an adaptation to strong winds.  Tree ferns such as Cyathus dealbata, C. medullaris, Dicksonia antarctica and D. squarrosa often dominate the forest undergrowth, and these in turn support many epiphytes such as the primitive Tmesipteris tannensis, and ferns such as Aspidium capense and Polypodium billardieri. Ferns are also a conspicuous feature of the forest floor with species like Asplenium bulbiferum, Lomaria lanceolata and Hymenophyllum demissum commonly occurring, and where there is a deep humus layer, orchids such as Acianthus sinclairii and Pterostylis banksii can be found.

Chathamian Tableland Forest

The most abundant trees of this formation are the two endemics Dracophyllum arborea (Epacridaceae) and Senecio (Brachyglottis) huntii (Asteraceae). The latter often providing spectacular displays of yellow blossoms.  Most of the remaining trees are also endemic including Coprosma chathamica (Rubiaceae), Corokia chathamica (Cornaceae), Myrsine chathamica (Mrysinaceae), Pseudopanax chathamica (Araliaceae) and Veronica gigantea (Scrophulariaceae). The lower tree layers are mainly dominated by the tree ferns Dicksonia antarctic and D. sqarrosa, and the whole lower forest is covered in epiphytic species especially filmy ferns such as Hymenophyllum multifidum, H. dilatatum and Trichomanes venosum

References

Balgooy, Van. M. M. J. 1960. Preliminary plant geographical analysis of the Pacific. Blumea, 10: 385-430.

Cockayne, L. 1958. The Vegetation of New Zealand. H. R. Engelmann (J. Cramer).

Cockayne, L. 1902. A short account of the plant-covering of Chatham Island. Transactions of the New Zealand Institute, 34: 243-325.

Molloy, L. 1994. Wild New Zealand. The MIT Press, Cambridge, Massachusetts.

Northcroft, E. F. 1975. Adventive flora of the Chatham Islands. New Zealand Journal of Botany, 13: 123-129.