PLANTS OF FRESH WATER, SWAMPS, AXD BOOS. 105 



CHAPTER VII. 



PLANTS OF FRESH WATER, SWAMPS, AND BOGS. 



Scarcity of aquatic plants in New Zealand Water-ferns The red Azolla The 



pond-weeds - - The water -milfoils - - Fresh-water algae - - Vegetation of hot 



springs Effect of plants on changing the land-surface Swamp vegetation 



The niggerhead Economic importance of swamps New Zealand hemp 



-Bogs and bog-plants Sphagnum and its peculiarities Flesh-eating plants 



A vegetable trap. 



IT has already been shown that in her forests, meadows, shores, and 

 shrubberies New Zealand possesses plants which do not yield in beauty 

 or interest to those of any other land. With her seaweeds, too, she is 

 well able to hold her own. But when it comes to the fresh- water 

 plants she must take a lower place. Rivers and lakes there are in 

 plenty which offer first-class inducements for occupation by aquatic 

 plants, but none of the more beautiful kinds have accepted the offer ; 

 in vain we look for water-lilies like those of the sister continent. Still, 

 for all that, our waters are not without plant-life, some of which, from 

 the biological standpoint, is interesting enough. 



THE WATER-FERNS. 



Take the case of the floating water-fern, Azolla rubra. The red 

 masses of this curious plant, covering still pools so thickly that one 

 might think them dry land, must be known to all. The outer surface 

 of the leaves is covered with minute excrescences, so that they cannot 

 be wetted, and, in consequence, drops of water frequently begem 

 them, glittering in the sunlight like diamonds. An individual plant 

 is quite small, and consists of a thin, much-branched stem, putting 

 down roots into the water from its under-surface, and bearing over- 

 lapping leaves. Each leaf consists of two lobes, which, except on 

 close examination, look like separate leaves. Each lobe is adapted 

 for a totally different condition of life, so there is a distinct division 

 of labour in the one leaf. The upper lobes are comparatively thick, 

 provided with leaf-green, and are therefore food-producers, and they 

 are never submerged. Each contains a large cavity full of slime, 



