154 | The Plant Formations. 
cerned is but 26, which belong to ı2 families and ı5 genera and comprise 
5 free-swimming plants, 8 soil-rooted and leaf-floating, 10 submerged and 3 
amphibious. 
On still waters throughout New Zealand proper, Stewart Island excepted, 
the floating water-fern, Azolla rubra, the individual plants only 1.2—2.5 cm 
long, forms close, red sheets several centimetres thick quite hiding the water- 
surface, which, by the inexperienced, might be mistaken for dry ground. Such 
an Azolla-association is generally quite pure, though it may occupy the water- 
surface of open swamp. The two floating species of Utricularia (U. protrusa, 
U. Masrii) are extremely rare, the former having been observed only on Lake 
Tongonge in the far N. and Lake Waihi (Waikato) and the latter may be 
extinct as it was noted only in the Lake Rotomahana which was destroyedby 
the eruption of Tarawera. U. protrusa forms floating colonies 60 cm or more 
across. ; 
Where the water is comparatively still and shallow, as near the margins 
of lakes and slow-flowing rivers, or on the surfaces of ponds and shallow 
streams, there are frequently wide breadths of the brownish, long-petioled 
leaves of Potamogeton Cheesemanü‘), their coriaceous, oblong blades some 
2.5 cm long, while, beneath the surface, there. are, in abundance, the short- 
petioled, translucent, ribbon-like leaves ‚generally slowly moving with the 
current. In similar stations are the amphibious Myriophyllum elatinoides and 
' M. propinguum forming masses of floating stems with submerged finely-cut 
leaves, but having also aerial stems with entire leaves ?.. Callitriche verna 
is another species of still water. | 
The submerged water-plants, some of which have been dealt with as 
coastal, are as follows: — Pilularia Novae-Zealandiae, FPotamogeton ochreatus, 
P. pectinatus, Zannichellia palustris, Althenia Preissei, Ruppia maritima and 
with these may perhaps be included Ranunculus Limosella and Glossostigma 
elatinoides. Re 
2 4. Swamp. : 
Br ‚a. General. N 
By swamp is here meant those plant-associations which occupy loose, 
frequently peaty soil, which is always more or less covered by a shallow layer 
of water. It is the representative, in New Zealand, of the “Niedermoor” of 
German and the “Fen” and “Carr” of English writers. Except forest, no 
formation has been so changed or eradicated by man, but, except in certain 
localities, areas, more or less unaltered, still persist, so that a general idea of 
New Zealand swamp may be gained, even if a detailed study is no longer 
possible. ; ee Evi ee 
1) 0r.08°2 natans or P, bolygonifolius as the case may be. Bann“ 
2) The handsome MM. robustum is included above in my estimate of aquatic plants 
it shows, at times, a certain amount of heterophyliy, but it. is dealt with under the heading 
