36 



The pteridophyte and spermophyte flora, limited as above, consists 

 of about 185 species belonging to forty-three families and ninety-six 

 genera. The most important to note of the species are the following, 

 which do not extend to the South Island ; some (marked with a star) 

 are very rare, or wanting, except in the Volcanic Plateau Botanical 

 District or its immediate neighbourhood : Ranunculus nivicola, Pimelea 

 buxifolia, Dracophyllum recurvum,* D. subulatum,* Logania depressa,* 

 Veronica laevis, V. tetragona* V. Hookeriana,* V. spathulata* Ourisia 

 Colensoi,* Euphrasia tricolor, and Raoulia australis var. albosericea 

 (= R. albosericea Col.). 



Coming to the vegetation, the most characteristic plant association 

 is that of the desert. That there should be such a feature of the 

 landscape in a forest climate seems a paradox. But it is not a 

 climatic but an edaphic desert, its presence depending on the porous 

 pumice soil, little retentive of moisture and easily moved by the 

 wind, and the loose scoria of the mountain-slopes. It is also, in 

 part, a primary stage of succession which has its climax -according 

 to circumstances in pumice fell-field, tussock-grassland, or -even 

 forest. In places there is retrogressive desert (e.g., part of the 

 Onatapu Desert). 



The most characteristic species of the association is Dracophyllum 

 recurvum, which forms reddish open cushions or almost mats. Fre- 

 quently the pumice sand blown by the wind builds dunes, which, 

 gaining stability through certain plants having secured a footing, 

 sometimes support more than twenty kinds of shrubs, herbs, semi- 

 woody plants, and grasses. The ultra-desert species which occupy, 

 at wide intervals, unstable slopes of scoria are Luzula Colensoi, 

 Claytonia australasica, Gentiana bellidifolia, and Veronica spathulata; 

 but elsewhere the Claytonia is often found at times in shallow water, 

 and the gentian under highly mesophytic conditions. 



Next in interest to the above is the pumice fell-field (named by 

 me originally " shrub-steppe ") occupying flattish ground at about 

 an altitude of 3,600 ft. to 4,500 ft. The plants grow on low, flat 

 mounds of fine pumice and humus. The usual species present 

 number twenty-five (fifteen shrubs, six semi-woody plants and herbs, 

 three tussock-grasses, and one fern). 



Tussock-grass^nd occupies much of the lower part of the open 

 country, with Danthonia Raoulii var. rubra dominant, and Dracophyllum 

 subulatum and the beautiful Euphrasia tricolor as characteristic species. 



Finally, the " winter-bogs " must be noted, where the plants 

 endure extreme conditions, since the habitat becomes dry in summer. 

 Carpha alpina, Oreobolus pectinatus, Hypolaena lateriflora var. minor, 

 and Celmisia glandulosa are common members of this peculiar 

 association. 



L.. COCKAYNE. 



THE GEOLOGY OF THE " MINERAL BELT " OF NELSON. 



The " Mineral Belt " of Nelson and west Marlborough is a great 

 band of magnesian igneous rocks, varying from six miles to about 

 half a mile in width, which stretches in a very definite and little 

 broken line for about seventy miles, from D'Urville Island at the 

 north-east of Nelson Province approximately south-westward to the 



