Forest. | | 141 
8. Semi-swamp Forest. 
In New Zealand, where there are extensive plains traversed by rivers rising 
in glacial mountains, floods must frequently occur, the water from which, in 
an undrained land, would but slowly recede, while some, gaining hollows, 
would remain permanent, forming shallow lakes or swamps. Not infrequently, 
too, low-lying forest would be flooded, so that new conditions would arise for 
the plants and those naturally possessing extra water-tolerating capacity would 
survive in the struggle for existence. In such areas, liable to flood, the slug- 
gish streams would be readily blocked by forest-debris and forest permanently 
wet be established. In time, certain species should become specially attuned 
to the semi-swamp life and new forms be evolved. The composition of a New 
Zealand semi-swamp forest supports the above statements, since there are two 
classes of species, the one consisting of quite facultative swamp-plants which 
also inhabit dry ground and another class which if not true obligates are 
almost altogether confined to situations subject to submergence either per- 
manent or for long periods. Then there comes a third class which are not 
characteristic of-such forests, but which occasionally occur, though probably 
only in the dryer ground. The following is a list of the species, taking the 
habitat throughout New Zealand, which belong to the first two classes: — 
(Semi- -obligate) Zycopodium . ramulosum, Laurelia novae-zelandiae, Rubus 
schmidelioides (juvenile form), Eugenia maire, Coprosma tenuicaulis, C. rigida; 
(facultative) Dicksonia squarrosa, Blechnum capense, Asplenium bulbiferum, 
Dryopteris pennigera, Gleichenia Cunninghamii, Podocarpus Halli, P. niwvalıs, 
P. dacrydioides, Dacrydium intermedium, D. Colensoi, Phyllocladus alpinus, 
Freycinetia Banksü, Microlaena avenacea, Gahnia setifolia, G. rigida, G. xantho- 
carpa, G. procera, Rhipogonum scandens, Astelia nervosa, Rhopalostylis sapida, 
 Paratrophis microphylla, Elatostema rugosum, Muehlenbeckia complexa, Drimys 
colorata, Carpodetus serratus, Melicytus micranthus, Leptospermum scoparium, 
 Myrtus pedunculata, Schefflera digitata, Nothopanazr anomalum, ee en 
ABU, Geniostoma ligustrifolium, ne: a a 
@. Kahikatea (Podacarpis daeryäiöides) forest. ER ne 
”  Kahikates forest occurs throughout New Zealand with the repligh u 
= the North Otago and Stewart districts in the latter of which there are only a a 
few trees in one or two localities. It is distinctly a lowland. community which 
 attains its greatest development near those large rivers which overflow their 
banks, though small typical areas occur anywhere on low-Iying swampy ground 
even, indeed, in dune-hollows. Although there are still wide areas of virgin 
forest, the great demand of late years for the timber of P. ee for 
