Pboc. Kot. Soc. Victoria 35 (N.S.), Pt. I., 1922.] 



Art. II. — On Coprosma Baueri, Endlicher. 

 By JOHN SHIRLEY, D.Sc, and C. A. LAMBERT. ; 



(With Plate IV.) 

 [Read 20th A2)ril, 1922.] 



1. The Genus. 



Coprosma is a genus of Rubiaceae, comprising some 60 species, 

 whose headquarters are in New Zealand. The Dominion and its de- 

 pendencies possess 39 of these species (1), Australia five (2), and the re- 

 maining units extend northward to New Guinea and Borneo, and 

 westward to the Sandwich Islands and Juan Fernandez, near the 

 Pacific coast of South America. The New Zealand species form dense 

 thickets, both in lowland forests and in woods to heights of 6000 

 feet. They vary very much in mode of growth and foliage at dif- 

 ferent periods of their life history. Many Coprosmas have the aspect 

 of desert plants, as have also New Zealand species of Pennantia, 

 Hohei'ia and Plagianthus, and are consequently termed xerophytes. 

 These show great range of variability in their leaves; the seedling 

 and mature stages possessing larger leaves than the intermediate 

 one. This xerophytic habit, so strongly represented in the flora 

 of a temperate, well watered group of islands, has been a fertile source 

 of discussion by biologists and geologists. Hutton(3) asserts that 

 during the Pliocene period the Southern Alps were much higher than 

 now, and that such groups as the Chatham and Auckland Islands 

 were part of the New Zealand mainland. The plains east of the 

 main ridge were arid and wind-swept, with warm summers, and very 

 cold winters. Dr. L. Cockayne (4) explains that the seedling stage of 

 these plants of xerophytic aspect, and with an alternation of leaf 

 forms, represents the ancestral plant before the Pliocene desiccation; 

 the intermediate foliage represents the plant of Pliocene New Zea- 

 land; and the larger leaves of the mature form are the response to 

 present conditions. Two erect species with large coriaceous shining 

 leaves are commonly cultivated in public and private gardens through- 

 out Australia — C. Baueri, Endl., and C. lucida, Forst. 



2. Previous workers. 



Cheeseman(5), in an article on "New Zealand Species of 

 Coprosma," refers to the curious little pits that exist on the under 

 surface of the leaves of these plants, states that they are often in- 

 habited by a tiny yellow acarid, but confesses that he is unable to 

 guess as to their function. 



Dr. A. N. Lundstrom (6) applied to the pits the name domatia, 

 and decided that they were of use to the plant as the home of com- 

 mensals, living in symbiosis with it. Mr. Alexander Hamilton (7) 



J The numbers refer to works consulted, shown in the Bibliography at the end of the paper 

 3a 



