Oliver. — Vegetation of the Kermadec Islands. 139 



Polystichum aristatum has a long creeping rhizome bearing at short 

 intervals erect, hard, dark-green, deltoid fronds, 1 m. tall. 



Dryopteris setigera is a tall fern, 1-2 m. high, with a short tufted rhizome 

 and few, light-green, delicate, compound, deltoid fronds. 



Diplazium japonicum is a low tufted fern, about \ m. tall, with few 

 light-green, delicate, pinnate fronds. 



Blechnum capense varies very much in its size and habit. It may be a 

 tall fern with erect fronds 2-2-5 m. high, or a low fern, | m. tall, with broadly 

 ovate or nearly orbicular spreading fronds. 



(c.) Ecology. — (1.) Ecological factors : First in importance of factors 

 determining both the existence and character of the forest is climate. An 

 abundant supply of rain spread throughout the year produces a forest 

 formation whose physiognomy alters in accordance with the amount of 

 moisture received. A full account of the climate has already been given. 

 The annual rainfall, amounting to over 1.700 mm. for nine months, and 

 high average degree of relative humidity, with a temperature never falling 

 below 8°C., and averaging more than 18° C, is ample to produce hygro- 

 phytic vegetation (16 ; p. 168), while the desiccating effect of the constant 

 ■winds is to a certain extent counterbalanced by the moisture-laden atmo- 

 sphere. The winds are most felt near the sea-shore and at the top of sea-cliffs, 

 where the vegetation is shorn down to a certain height, above which nothing 

 but dead twigs project. 



The general effect of the warm and humid climate on the vegetation is 

 to promote a luxuriant growth. This is exemplified in the case of New 

 Zealand plants extending to the Kermadecs. Macropiper excelsum and 

 MeUcope tcrnata are each represented by varieties characterized by larger 

 leaves. Corynocarpus Icevigata and Myoporum IcBtuni, small trees in New 

 Zealand, are on Sunday Island lofty forest-trees 20 m. tall. The habit of 

 two plants — Calystegia SoldaneUa and Ipomcea palmata — of flowering but 

 not fruiting (according to my observation) is perhaps occasioned by the 

 climate. Some mosses rarely bear fruiting capsules. 



A number of plants flower immediately after fruiting. In the case of 

 Rapanea kermadecensis both flowers and ripe fruit ai'e sometimes seen 

 on the same twig. Besides this species, Coprosma petiolnta, C. acutijolia, 

 Macropiper excelsum major. Ascarina lanceolata, and MeUcope ternata flower 

 during the winter months. The slight fall in temperature, rather than 

 interfering with, seems to favour the development of the reproductive 

 organs (see 16 ; p. 48). 



In the list of indigenous plants I have recorded the measurements of 

 large specimens of several plants. 



The most noticeable effect of winds is to limit the general level of the 

 vegetation in exposed places. Myoporum Icehim, which is the principal 

 plant in the coastal scrub, adapts itself precisely so as to offer least resistance 

 to the prevailing Avinds. Its slanting flat top is maintained by the constant 

 wi)ids, which, laden with salt spray, kill every twig above a certain level, 

 <letermined by the density of the foliage. ' On the tops of cliffs, where the 

 wind strikes with full force, the foliage is shorn down to a certain height, 

 above which only dead twigs project. 



Soil is a factor second in importance only to climate. There is little 

 variety of soils on Sunday Island, any difference between one and another 

 consisting in the proportions of vegetable matter contained in each. The 

 soil everywhere consists of the more or less altered — by weathering and 



