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PACIFIC SCIENCE, Vol. IV, July, 1950 
This is an association which occurs con- 
stantly in all areas except where there is very 
strong wave action, and which is characterised 
by a distinctly restricted vertical range (about 
18 inches). Both the dominants are impor- 
tant because they eliminate larger algae that 
otherwise might be present. 
6. Gigartina alveata consociation ( Fig. 3 ) 
Range: M.S.L. to M.L.W.N. 
Gigartina alveata (d) 
Modiolus neozelanicus (If) 
Chamaesipho columna (f) 
Gelidium caulacantheum (la) 
Pleonosporum hirtum (summer) 
Scytothamnus australis (o) 
The consociation forms a compact belt in 
those places where there is neither strong 
wave action nor extreme shelter. It always 
occurs above Pachymenia himantophora when 
both are present. On boulders at the head of 
gullies the community tends to be closed so 
that there are very few, if any, associated al- 
gae. In wave-exposed situations bleached and 
stunted specimens of Gigartina are scattered 
sparsely over the rocks. 
7. Pachymenia himantophora consociation 
(Fig. 4) 
Range: E.(H) .L.W.N. to about 12-18 
inches below. 
Pachymenia himantophora (d) 
Lcphurella caespitosa (o) 
Champia novae-zelandiae 
Gelidium caulacantheum (o) 
The consociation is absent in the more 
sheltered localities of the open coast, and ap- 
pears to reach its maximum development in 
gullies where the plants are exposed to heavy 
surge as distinct from breaking waves. On 
the open coast it occurs on the shoreward side 
of rocks with Durvillea at the same level on 
the seaward side. 
8. Gigartina marginifera consociation 
(Fig. 4) 
Range: M.L.W.S. upwards for 6-9 
inches. 
Gigartina marginifera (d) 
Steno gramme interrupta (o) 
Champia novae-zelandiae (o) 
Carp op hy llum mas chalo carpus (1) 
The consociation occurs below the Pachy- 
Fig. 3. A view of Gigartina alveata consociation with Modiolus neozelanicus. 
