Ecological Botnmj.'] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 191 



Tlie moisture-laden atmosphere and lack of sunshine at all seasons strongly 

 favours the formation of peat.* The dead leaves and stems of the herbaceous plants 

 slowly rotting remain attached to the living plants ; biyophytes on the ground, on 

 tree-trunks, on rock-faces build thick layers and cushions of ])^&t, the outer shoots 

 alone alive ; so, too, with the spermaphytic cushion plants. The ferns Blechnum 

 durum and Asfleninm ohtusatum, so common on the coastal cliffs, form from their 

 dead rhizomes masses of peat 30 cm. or much more in depth, which completely 

 cover the flatter rocks, and even at times the almost vertical faces of coastal cliffs, 

 so that a luxuriant plant-covering exists. Indeed, the whole soil of the islands, 

 sometimes for a depth of 30 ft. or more, is made up altogether of plant-remains, and 

 contains no outward sign of mineral matter.f Such a soil becomes extremely wet, 

 being frequently quite saturated ; in many places pools of water lie upon its surface, 

 and holes, masked by the vegetation, but full of water, are everywhere on the open 

 hillsides. Even during the brief periods of sunshine, tussock meadow and scrub 

 are dripp)ing wet, so that one's clothes quickly beeonae saturated. 



The saturation of the soil, its very imperfect drainage, the scarcity of free oxygen, 

 and the absence of micro-organisms lead to an abundance of humous acids in the 

 substratum. These acids on the one hand, and the coldness of the soil on the other, J 

 a matter due not to frequent and long-enduring frosts, but to the ever-present wind 

 acting on a wet soil, lead to a marked physiological dryness which is clearly reflected 

 in the xerophily of so many of the life-forms. The vegetation is. generally speaking. 

 more or less of a moorland character, the maximum being exhibited by the mountain 

 bogs, and the minimum by the rata forest and PleurophiiUiDit meadow ; indeed, this 

 latter term is by no means ecologically appropriate, but is used throughout this 

 paper rather to keep the nomenclature in line with my former writings than be- 

 cause any natural New Zealand plant formation is truly a meadow in the European 

 signification. 



The plants themselves — that is, more esjjecially th(^ life-forms evoked by the 

 climate — are not without considerable influence on distribution. The interior of the 

 rata forest is markedly hygrophytic ; the robust tussocks of the meadows shelter 

 ground-plants, and even shrubs, providing an almost wind-still atmosj^here. On 

 Antipodes Island, whilst a fierce gale was in progress, seated beside a tussock on the 

 exposed summit of a ridge, all was calm and still, though overhead the raging of the 

 storm could be heard (Cockayne, ''Botanical Excursion," p. 293). 



The indigenous animals, especially the penguins and albatroses, have, particu- 

 larly in some of the smaller islands, a good deal to do with plant-distribution, through 

 destroying the existing vegetation and preparing new ground for plant-colonisation 

 and rearrangement of the species. This interesting matter is gone into at some 

 length under another head. 



* Sec also Darwin, " A Naturalist's Voyage," pp. 286-87 (edition of 1889). 



I The nitrogen content is usually very great, according to Aston (Annual Report Department of 

 Agriculture for 1908, "Soils from the Southern Islands," pp. 310-11; 1909), reaching in one case 

 2-92 per cent. ; but probably the amount available for the plants is in many places quite small. 



± Dachnowski (Bot. Gaz., vol. xlvii, p. 389 ; 1909) is of opinion that xerophily in bog-plants is in 

 part due, at any rate, to the presence of certain deleterious substances, which he calls " bog toxins," 

 produced in the soil as the result of a number of chemical and physical factoi's. See also Livingstone, 

 B.E., " Physiological Properties of Bog Water," ihid., vol. xxxix ; 1905. 



