Cockayne — Observations on Coastal Vegetation. 325 



aspect of the case. I refer to those southern plants which only 

 reach a certain distance northwards. Senecio rotundifolius is 

 an example. This, as will be seen further on, is an important 

 constituent of a somewhat local plant formation found in the 

 south-west of the South Island. It is also abundant in Stewart 

 Island, but is not found on the east of the South Island at all, 

 although many stations are most suitable, nor is it found on the 

 west coast beyond latitude 44°, or on the south coast beyond 

 the eastern boundary of Bluff Harbour (14b). Yet on the east, 

 this plant, cultivated at Dunedin, forms magnificent hedges, 

 while it is gi'own with success even as far north as Auckland 

 City. Here there is, then, no question of frost, or even of any 

 damage from a hotter summer climate ; if there is any inhibitory 

 climatic factor in this case it would be rather a question of want of 

 moisture. A still more interesting example is Veronica elliptica. 

 This plant, which is also a native of Tierra del Fuego, is a most 

 common feature of coastal rocks and cliffs in the southern part 

 of the South Island, and it extends even to the far-off Auck- 

 land and Campbell Islands. But in the northern part and north- 

 east of the South Island it is quite wanting, nor does it occur 

 at all in the North Island or the Chatham Islands, in both of 

 which, however, there are rock-loving veronicas. Now, although 

 this is a strictly southern plant, being identical possibly with 

 the Fuegian species of the same name, it cannot, as shown above, 

 tolerate much frost.* This species, then, seems more suited to 

 the warmer north, and yet, as stated above, it is quite wanting 

 in the North Island. The distribution of Crassula nioschata, 

 too, is interesting. This low-growing succulent herb, a native 

 also of the Fuegian region, occurs in abundance on the Southern 

 Islands. In the South Island it is common in the south and 

 south-west, but further north it is quite local, wide reaches 

 of coast being destitute of this species, although so far as station 

 and climate go they are quite suitable. It occurs sparingly on 

 Banks Peninsula, and then, so far as I know, is not found again 

 until the shores of Cook Strait are reached, which it crosses, and 

 is finally found in the neighbourhood of Island Bay, Wellington, 

 and its vicinity, but does not occur further north. 



From the above cases it seems evident that extremes of 

 climate is only one of the factors with regard to the distribu- 

 tion of coastal plants in New Zealand. Rather, perhaps, than 

 heat or cold alone is the matter one of the ecological optimumf 



* A plant of Veronica elliptica, originally from the Bluff, grown in my 

 former garden near New Brighton on an ancient sand-dune since 1897, 

 has never thriven, being yearly cut back by frost. 



t For explanation of this t«rm see Schimper (41 ; p. 44). 



