sale I GE Sa a S  aien  n A 
n „Lich 
ET u Ne RZ 
Fer 
ae 
65 
Bi ee, botanical district. (Plate IV, Fig. 5). 
muddy sdbstratum which, thougt 
Fr overlie rock. 2. Absence of fr 
 erosion of insufficient ‚power t > 
? SH In places, very shall 
lie on the the 
Brakish-water Associations. — Salt Swamp, © 
a b. Zostera association. 
There are two species of Zostera in New Zealand, Z. nana and Z. tas- 
manica'), the former making a pure association between tide-marks and the 
latter being permanently submerged. 
£. nana forms extensive grass-like colonies on the muddy floor of estuaries 
in all the botanical provinces. The association is uncovered only at spring 
tides, the grassy leaves Iying on the mud, through which creeps the slender 
brittle rhizome. 
2. Brackish-water submerged Associations. Me 
Ruppia maritima forms submerged masses of filiform stems and laves 
on the floor of lagoons &c. and slowly-flowing streams in somewhat ee £ 
water. 
Althenia bilocularis, a smaller plant of similar siöwihlocmn, also oceurs in 
some localities on the east of the South Island under identical conditions. 
Zannichellia palustris, another ecologically equivalent eye occupies 
similar stations to the above. 
3. Salt Swamp. 
a. Mangrove swamp (Tidal forest or scrub). we 
In New Zealand this formation possesses but one species, Avicennia Da a 
feinalis, which forms belts or patches of scrub or low forest, as the case may 
be, between the tide-marks in shallow estuaries, tidal rivers, sheltered bays and 
the like. It is restricted to the Northern botanical province and is to be seen 
in its greatest luxuriance in the extensive estuaries and tidal rivers of ba Ban 
The presence of the formation depends chiefly upon the en 
ar 
is light. brown on el 
