198 PLANTS OF NEW ZEALAND 



in the neighbourhood of Rubiis. The correct explanation is 

 given by 1 Kerner. It is, perhaps, worth quoting : — 



" A plant distinguished by its unusually rich development of 

 barb-hke spines, and deserving special mention here, is the 

 New Zealand bramble, Bithua squarrosus (R. cissoidcs). 

 Each of its leaves is divided into three portions, each being 

 provided with a tiny blade at its apex ; these three portions, 

 as well as the leaf-stalk, are green throughout their entire 

 length, and beset with yellow pointed prickles, which anchor 

 so firmly in the intertwined bushes and shrubs, that a wholly 

 inextricable tangle is the result." 



The passage quoted is provided with a good illustration of a 

 spray of B. cissoides. 



Some confusion has also been caused in the determination 

 of the species, by the neglect of most botanists to notice 

 carefully enough the relation between the form of the plant 

 and its habitat. 



Df. Cockayne has, however, given a full account of the 

 development of R. cissoides'''' and a description of the various 

 forms which it assumes. Like the other New Zealand 

 species, in the forest it is a liane climbing by prickles, 

 and there it is provided with lanceolate acuminate leaflets. 

 The flowers are yellowish, and the fruit red. When found 

 in the open, it is a leafless mounded bush, consisting of 

 intertwining stems and midribs, with fai- more numerous 

 prickles, than it has, when growing in the forest. This 

 is the stage described above by Kerner. An extraordinary 

 fact about this depauperated form is, that it has never been 

 known to produce flowers or fruit. This is probably due 

 to tlie fact that the leafless plant is merely an arrested stage 

 in the development of the mature form. Dr. Cockavne 

 has also suggested that the absence of flowers may be due 

 to the destruction of the young growing points in exposed 

 situations. 



tNatin-al History of Plants. I., 677 (Enylish Translation.) 

 •Trans. XXXIII., p. 2«1. 



