Martin. — Pteridophytes of Banks Peninsula. 315 



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 Art. XXXll.—Pterido'phytes of Banks Peninsula (Eastern Portion). 



By W. Martin, B.Sc. 



[Read before the Philosophical Institute of Canterbury, 3rd December, 1919 ; received by 

 Editor, 31st December, 1919 ; issued separately, 30th June, 1920.] 



Owing to its isolated geographical position, Banks Peninsula affords special 

 opportunity for ecological investigation, yet few botanists have given it 

 the attention it invites. Our present knowledge of the florula and of the 

 distribution of the species has been admirably summed up in a recent paper 

 by Laing (1919). 



In his list of indigenous plants Laing refers to a large number of 

 species of the former existence of which there can be little doubt, but whose 

 presence is not now known with certainty. Such plants are recorded as 

 " species inquirendae." Reference is also made to a number of species 

 recorded by previous investigators, regarding the identification -of which 

 some doubt is expressed. Laing describes these as " species excludendne." 

 It therefore seems desirable that an intensive study of the plants of this 

 district should be conducted before further denudation of the primitive 

 vegetation takes place. 



Laing in his paper expresses the hope that " before the remnants 

 of the primitive flora disappear every opportunity will be taken by local 

 students to complete the work here outlined." The scope of the present 

 paper is limited to an investigation of the past and present distribution of 

 the pteridopyhtes of the Akaroa caldera and its immediate neighbourhood. 

 The district examined consists of that portion of Banks Peninsula lying 

 to the east of a line joining Peraki and Pigeon Bay. Practically every 

 remnant of the ancient forest within the caldera itself has been visited 

 since December, 1916, as well as the majority of similar areas that flank 

 the outer walls. Most of the accessible cliffs within the harbour have 

 also been examined, but the whole of the slopes facing the open sea require 

 further and closer examination than I have been able to give to them. 



The earliest existing records of distribution are contained in the writings 

 of Raoul (1846), Armstrong (1880 and 1882), and Potts (1882) ; but for 

 much additional information I am specially indebted to Mr. D. G. Riches, 

 of Akaroa, who since about 1880, while engaged on survey work that took 

 him to everv corner of the area under discussion, has been a close student 

 of the ferns of Banks Peninsula and has made copious collections exclusively 

 from this area. Many of the localities cited by Riches have been corro- 

 borated by Mr. Louis J. Vangioni, of Akaroa,' and Mr. George Penlington, 

 of Christchurch, to both of whom I am indebted for valuable information. 

 In several instances I have been able, from information thus obtained, 

 to locate ferns included by Laing in his list of doubtful inhabitants. 

 Species recorded in this paper are represented by specimens from the 

 localities named, and now in the possession of Mr. Riches or myself. 



Probable Causes op Diminution or Extinction of Species. 



Before the days of colonization the hills about Akaroa were clad with 

 forest right to the water's edge, and it seems safe to assume that the 

 atmosphere was more humid than it now is ; but even if the annual 



