382 Transactions. 



water."* This is just a natural application of the laws ruling 

 the phenomenon of osmosis. When the root absorbs water with 

 difficulty it is necessary to reduce the amount transpired from the 

 leaves, and hence those modifications of the leaf to check trans- 

 piration. The soil is also usually poor in oxygen, and this added 

 to its acid character renders absorption of water difficult, and 

 again necessitates the xerophytic character in the leaf. " The 

 water-capacity of a given soil does not enable us to judge of the 

 quantity of water that a certain plant is capable of taking from 

 it."* 



In considering the adaptability of the plants to their en- 

 vironment, I will first of all deal briefly with some common fea- 

 tures of external form which aid the plant in its struggle. 



The strong winds to which certain parts of the islands are 

 subjected must necessarily have a corresponding effect in deter- 

 mining the nature of the plants. Thus, for instance, there is 

 an absence of any arborescent species on Campbell Island and 

 Antipodes Islands, where there is greater exposure to such gales 

 than on the Snares and in the Auckland Group. The trees that 

 are present show the direction from which the winds come in 

 the stunted branches on the windward side. The small species 

 of the Coprosmas which occur on all the islands except Macquarie 

 and Bounty Islands show the tendency to avoid exposure to 

 the wind's by their prostrate habit. Amongst the herbaceous 

 plants, a large projuortion form rosettes of leaves, which, pressed 

 closely to the substratum, are able to resist the dislodging effects 

 of furious gales. The huge plants of Pleurophyllum have adopted 

 this habit, and form wide-spreading rosettes " which cover acres." 

 The smaller genera, Abrotanella, Cotula, Gentiana, Myosotis, and 

 Plantago, may also be classed here. Others have prostrate stems 

 creeping over the ground and rooting at intervals ; amongst 

 these may be mentioned Epilobium, Cotula, and Pratia. Others, 

 again, as the grass-like forms, Luzula, Scirpus, Carex, and Poa, 

 are able to withstand any ill effects from the wind by their thin, 

 linear, and pliant leaves. The larger herbaceous plants, as the 

 two species of Ligusticum and the large-leaved Stilbocarpa, are 

 able by the stout and firm structure of their leaves to resist the 

 wind. 



The modifications of the leaf itself to check transpiration 

 may be enumerated as follows (following chiefly Kearney's classi- 

 fication, 1900, p. 279) :— 



(1.) A reduction in the transpiring surface, in the two species 

 of Coprosma. 



(2.) The position of the transpiring surface — modification 



*Schiinper (1903), p. 85. 



