544 Transactions. 
as an undergrowth. There is also an association of Scirpus americanus, 
Triglochin striatum, and Paspalum distichum, with Helice crassa, Amphibola 
crenata, and Potamopyrgus antipodum. 
MANGROVE Formation. 
Mangrove is a formation of woody plants growing in mud between tide- 
marks, and includes, besides shrubs, a surface and subsurface marine fauna. 
The animals are similar to those of the adjacent mud-flats, but apparently 
poorer in species—at least, in the only locality that I examined. Very 
interesting ecological relations have been described for mangrove, but onl 
two points will be mentioned here. In Avicennia officinalis horizontal 
roots below the surface of the mud give off many erect peg-like pneumato- 
phores projecting to 30cm. or so above the mud and functioning as 
respiratory roots. As a provision for quickly becoming fixed in the mud 
the embryo before it falls from the tree germinates as far as bursting the 
seed-coat, providing rudimentary roots and green cotyledons. An account 
of the New Zealand mangrove has been given by Cockayne (1921, p. 65; 
also N.Z. Plants and their Story, p. 35, 1919). Further details of the 
ecology of mangrove formations, with references to literature, will be found 
in the works of Warming (1909, p. 234) and Schimper (1903, p. 395). 
Mangrove is found in New Zealand in all tidal estuaries and inlets as far 
south as Kawhia and Tauranga Harbours. (Plate 50.) 
Auckland Harbour.—In Shoal Bay the mangrove is small, but all of 
even height—about 1 m. It covers an extensive area near the level of 
land edge of the mangrove, Potamopyrgus antipodum, Phytia ornata, and 
small amphipods are abundant. 
IV. LITERATURE. 
ALGAL COMMUNITIES. 
1897. Kuoxvok, P., Beitraege zur Kenntniss der Meeresalgen Wissensch., Meeresunter- 
suchungen, N. F. Bd. 2. ; 
1898. Sommerer, А. Е. W., Plant Geography upon a Physiological Basis. English 
edition ; Oxford, 1903. ч 
1909. WanMrNG, E., and Vanr, M., Oecology of Plants. English translation ; Oxford. 
1912. Corton, A. D., Clare Island Survey, Part 15, Marine Algae, Proc. Roy. Irish 
Academy, vol. 31. 178 pp. : 
