ER 155 
Swamp originates in various ways, the most common being from the 
gradual occupation of lake by aquatic plants in the first case and swamp- 
species in the second, or from rivers frequently and regularly overflowing their 
banks. In any case, through the decay of the dead plants, in course of time, 
considerable accumulation of peat takes place, a sour soil is produced and 
bog-conditions may follow; but, on the other hand, swamp-tolerating shrubs, 
and then trees may enter the association, and, as already described, first 
swamp-forest and then ordinary forest form a climax. Also, of course, there 
may be the reverse. 
The number of swamp-species excluding aquatics is about 65, which be- 
long to ı6 families and 32 genera; their growth-forms and the number of 
species in each are: — trees ı, shrubs 8, herbs 13, lianes ı, grass-like plants 
16, rush-like 24 and ferns 2. Besides many typical helophytes, e. g., the major- 
ity of the grass- and rush-like plants, there are xerophytic shrubs (Carmichaelia 
paludosa, Dracophyllum virgatum, Coprosma propingua, Olearia virgata) and 
mesophytic shrubs (Veronica salicifolia and its var. paludosa, Coprosma Cunning- 
hamit). About 36 species are virtually confined to swamp, many of the re- 
mainder occur principally in wet ground, but 3 species, at any rate, occupy 
‘ordinary mesophytic or even strongly xerophytic stations. The Kadian physio- 
gnomic plants are: — 7ypha angustifolia vars. Muelleri and Drownii, Carex 
secta, Phormium tenax and Leptospermum scoparium. 
b. Reed-Swamp and its allies. 
ı. Raupo (Typha)-association. 
; This association dccurs in abundance from sea-level to an altitude of 750 m 
on all kinds of soil, including sand, so long as covered with water all the 
year round; it is absent in Stewart Island. The 7yp4a may dominate, or 
Phormium tenax be present in equal quantity; in any case, the former is the 
Ä corner and can occupy water too deep for the well-being of Phormium. 
= the other hand, natural or artificial draining leads to the dominance 
a of Phormium which thrives. far better on a rich,  well-drained soil than in 
swamp. 
| The following species, bundaht in the Northern Basic province, occur 
also, to some extent, in the North Island portion of the Central Province, but 
are rare or absent in the South Island: — Sparganium antipodum (rare in 
 North-western district), Isachne australis (to Volcanic Plateau and N. of Eg- 
. mont-Wanganui districts), Zlaeocharis sphacelata (occasionally on W. of South 
Island to Stewart Island), Cladium articulatum (E. Cape district, 
“ ‚A well-developed Raupo-swamp, in the N., consists of close-growing The, 
1.8 m or more high, their leaves pale-gren, 5 stout and erect. There will be 
‚dense en of Isachne, australis : a shoots intermii 
“ 
