42 Transactions. 



actual dividing-range. The lowland form of the plant growing near the 

 sea-cliffs at Charleston, west Nelson, is also distinct in appearance. 



2. Isolation. 



This special form of distribution is considered by some to be of the 

 greatest evolutionary importance. The New Zealand biological area offers 

 many ideal localities for geographical isolation, differing in degree, and it 

 is interesting to see as to how far they afford examples of related species 

 which appear to have either diverged recently from a stem form, or one 

 of them to be the actual parent plant. 



(a.) The Kermadec Islands. 

 The total number of species of vascular plants is 114, of which twelve 

 are endemic* These latter, one excepted, are closely related to, and in 

 some instances almost identical with, New Zealand, Polynesian, or Norfolk 

 Island plants. 



(b.) The Three Kings Islands. 



There is strong geological evidence that at no distant date these islands 

 were united to the North Island. | The total number of species of vascular 

 plants is 143, of which five are endemic ; with these Alectryon excelsum 

 Gaertn. var. grandis Cheesem. may be included. Coprosma macrocarpa 

 Cheesem., one of the five, is related to C. grandifolia Hook, f., and more 

 distantly to C. robusta, both of which are present on the island. Pittosporum 

 Fairchildii Cheesem. is allied by P. crassifolium A. Cunn. and P. umbellatum 

 Banks & Sol. Veronica insularis Cheesem. is related to V. diosmaefolia 

 R. Cunn., a species of the neighbouring mainland, and Paratrophis Smithii 

 Cheesem. to P. opaea Brit. & Rend., while the fern Davallia Tasmani Field 

 is not allied to any New Zealand species. None of the endemic plants, 

 then, except the Alectryon, are particularly close to their mainland allies. 



(c.) The North Cape. 



This high promontory was undoubtedly quite recently an island. There 



are three endemic plants — Halorrhagis cartilaginea Cheesem! (a near relative 



of H. erecta Schind.), Geniostoma ligustri folium A. Cunn. var. crassuiu 



Cheesem., J and Cassinia amoena Cheesem. (probably related to C. Vau- 



villiersii Hook, f., but which latter is not found nearer than the volcanic 



plateau). 



(d.) Islands lying to the Eastward of Auckland. 



Veronica Bollonsii Cockayne, a species closely related to V. macroura 

 Hook, f., is endemic on the Poor Knights Islands. Pittosporum inter- 

 medium T. Kirk, intermediate between P. tenuifolium Banks & Sol. and 

 P. ellipticum T. Kirk, is found only on Kawau Island ; only one plant 

 has been found, and this has been destroy ed.§ 



(e.) The Chatham Islands. 

 The total number of species plus named varieties is 236, of which thirty- 

 one are endemic. The genera Myosotidium and Coxella are endemic and 

 monotypic. The following is a list of the endemic plants ; those related 



* See Oliver, 1910, p. 150. 



t See Cheeseman, 1891, pp. 419, 420. 



t Were not Mr. Cheeseman extremely cautious regarding the " creation " of 

 species, &c., I should suspect this to be simply an unstable xerophytic form not very 

 different from that with thick leaves common on the lava of Rangitoto Island. 



§ Cheeseman might consider this a hybrid were it not that P. ellipticvm is not 

 known either in Kawau or the neighbourhood (1906, p. 54). 



