12 NEW ZEALAND PLANTS. 



aquatic plants, and these would in time become hereditary. This 

 latter theory is mentioned because a number of New Zealand species 

 appear to afford some confirmatory evidence. 



PLANT SOCIETIES. 



The plants having come to New Zealand, having fought many 

 battles, and having in numerous cases given rise to new species, their 

 final settling-down might, at the first glance, seem the work of blind 

 chance. Yet it was nothing of the kind. 



A seed falling upon any piece of ground would, if it germinated, 

 depend for its subsistence upon its power to make the best of the 

 circumstances. Were other better-equipped plants present, the 

 species in question would be wiped out. Also, w r ere its structure 

 and organs not suitable for living under the conditions provided, it 

 would soon vanish even were there no competition. In consequence, 

 soil and climate exercise a selective power, and so permit various 

 species of plants to live together under a definite set of conditions. 

 Thus have come into being those collections of plants known as plant 

 societies or associations,* ' which, taken all together, make up the 

 vegetation of New Zealand. These societies are sometimes quite 

 distinct in themselves, but frequently they merge into one another, 

 just as that human society called a town merges into the adjacent 

 farming community by way of the suburbs. 



The two most important groups of plant societies are forests and 

 grass-land. There are numerous varieties of both in New Zealand- 

 and some of them are described further on. Another large class con- 

 sists of those societies which depend upon the presence of an excess of 

 water in the soil, as in swamps and bogs ; while some plants float upon 

 the water of streams or lakes, or are quite submeiged. Others owe 

 their presence to the very opposite set of circumstances scarcity of 

 water ; and even in humid New Zealand something like a desert 

 vegetation may be found in not a few places, but its presence depends 

 rather on the nature of the soil than on an insufficient rainfall. Then 

 there are the societies peculiar to the sea-coast, where salt in the 

 soil and exposure to strong winds are important factors. In such 

 places are sandhills, salt meadows and marshes, shingly or sandy 

 beaches, and cliffs. Rocks have societies of their own, and some- 



* Also called by some " plant-formations," but there is no uniformity as yet 

 in the use of this term. 



