328 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1949 
public, or an untouched natural research laboratory to the scientist? 
Able protagonists have arisen to fight for its preservation from com- 
mercial exploitation (21). 
The many complexities and variations in the mixed dicotylous- 
taxad forest can only be suggested here. Such a forest may be a rimu 
forest with the ‘‘red pine” (Dacrydium cupressimum) dominant, a 
totara forest with Podocarpus totara dominant, or a tawa forest with 
the principal trees Beilschmeidia taraire or B. tawa of the dicotyledon- 
ous family Lauraceae, though usually with Podocarpus or Dacrydium 
also present. These forest types intergrade and vary extensively, so 
it is often difficult to determine just what kind of tropical forest one 
finds himself in. 
The parallels of 38° and 42° south latitude are significant as the 
southern limits of quite a number of species and the northern limits 
of others. As noted above, the kauri ceases at about 38° south. 
Some of the 100 or so others which drop out at this point are the toru 
(Persoonia toru—Proteaceae), the white-flowered tawari (Izerba breri- 
oides—Saxifragaceae), the climbing fern (Lygodium articulatum), and 
the trailing fuchsia (Fuchsia procumbens—Onagraceae). The 42d 
parallel, where many other species drop out, cuts off the northern end 
of South Island. The fact that this unnatural boundary does not co- 
incide with Cook Strait between North and South Islands suggests 
the geologically recent separation of the islands. 
In addition, certain plant forms drop out at various points. For 
example, the numerous epiphytes of the mixed rain forests of the west 
coast of the South Island are conspicuously lacking in the rain forests 
of Banks Peninsula, the vicinity of Dunedin in Otago, Southland, and 
Stewart Island. The composition of these mixed rain forests changes 
also with variations in the atmospheric humidity, the soil moisture 
and composition, the altitude, and perhaps the geological and biological 
history. The dicotylous-taxad association of the better-drained land 
gives way to a much more pure association of ‘‘ white pine,” kahikatea 
(Podocarpus dacrydioides) in poorly drained or swampy lands, as 
formerly existed in some prominence in Canterbury on the dry side 
of South Island. Here the deleterious effect of the drier air, inimical 
to the best growth of most rain-forest trees, was compensated for by 
the greater and more steadily available ground water. The swamp- 
land forests of Stewart Island are dominated by another tree, Dacry- 
dium intermedia. Altitude, or the changed environmental factors 
that go along with changes in altitude, also cause changes in this 
mixed association. As it rises higher on the mountains it is gradually 
replaced by southern-beech forests. On Mount Egmont, however, 
they give way to another altitudinal forest association composed of 
kamahi (Weinmannia racemosa—Cunoniaceae) and the New Zealand 
