The principal ecological factor determining the presence of 

 true coastal species is an excess of salt in the soil above that 

 which ordinary inland plants can tolerate. Thus the plants 

 of salt-swamp, salt-meadow, seashore, and rocks exposed to sea 

 spray are mostly actual coastal species, e.g., Arthropodium 

 cirratum, Atriplex Billardieri, Atropis stricta, Avicennia 

 officinalis, Carex litorosa, Crassula moschata, Mesembryanthe- 

 mum australe, Mimulus repens, Rumex neglectus, Salicornia 

 australis, Sonchus littoralis, Suaeda maritima. But the follow- 

 ing characteristic coastal, salt-tolerating species occur in one or 

 more localities far inland : Eryngium vesiculosum, Juncus 

 maritimus var. australiensis, Leptocarpus simplex, Scirpus 

 americanus, Selliera radicans, Triglochin striatum *var. fili- 

 folium, Apium filiforme and Samolus repens var. procumbens. 



The comparatively mild climate of the coast as compared 

 with that further inland is responsible in part, at any rate, for 

 the presence of species which cannot tolerate much frost. To 

 this category the following probably belong: Avicennia 

 officinalis, Coprosma Kirkii, C. retusa (C. Baueri of the Manual), 

 Corynocarpus laevigata, Dodonaea viscosa (in the southern part 

 of its range), Dysoxylum spectabile (in the southern part of its 

 range), Entelea arborescens, Hymenanthera novae-zelandiae, 

 Macropiper excelsum (in the southern part of its range), 

 Myoporum laetum (in the southern part of its range), Olea 

 apetala, Paratrophis opaca, Pisonia Brunoniana, and Sideroxylon 

 novo-zelandicum. 



Moving dunes present uncommon conditions demanding 

 special growth-forms for their plant inhabitants and sucfr swell 

 the list of purely coastal plants. There are the major sand- 

 binders: Scirpus frondosus, Spinifex hirsutus and Euphorbia 

 glauca; the minor sand-binders, Calystegia Soldanella and Carex 

 pumila; and the sand-collectors, Cassinia retorta, Coprosma 

 acerosa, Pimelea arenaria and P. Lyallii 8 , this also a sand- 

 binder to some extent. 



There are many different coastal plant-associations besides 

 those already mentioned, some of which (forest and shrub 

 associations) are dealt with when treating! of distribution in 

 regard to latitude. 



(2) THE LOWLAND FLORA. 



The lowland flora (including in this term the flora of the 

 lower parts of the mountains up to 2000ft. altitude as an aver- 

 age) contains about 1009 species, of which some 517 are purely 

 lowland, 350 (many extremely common) also belong to the high 

 mountains, 100 are virtually high-mountain plants but they 

 occur in the lowlands under special circumstances, and 42 are 



8- Here the view is taken that the name Pimelea Lyallii be restricted to the 

 sand-hill plant of the South Otago'and Stewart Districts and that the high- 

 mountain plants formerly referred to this species fall into one or more unnamed 

 species, excluding the bushy shrub of Central Otago which I am naming elsewhere 

 Pimelea aridula. 



