COOK STRAIT NOT A BIOLOGICAL BARRIER. 185 
composed of tawa (Beilschmiedia tawa); southern-beech forest is 
generally absent, Nothofagus Solanderi, when present, being frequently 
confined to the crest of ridges. The high-mountain flora of Mount 
Egmont is considerably smaller than that of the Volcanic Plateau 
or of the Ruahine-Tararua Ranges. 
As farmland the soil grows grass amazingly, so that certain areas 
produce almost unbelievable amounts of cheese and butter. At the 
Kaupokonui Cheese-factory, for instance, 2,500 tons of cheese are 
produced from the milk of ten thousand cows grazed on less than 
20,000 acres. The mild, moist climate allows camellias, azaleas, and 
many other flowering-shrubs to grow to a size uncommon elsewhere 
in New Zealand, and to bloom with the greatest profusion. Near 
the coast and for some miles inland the immense hedges of the 
African box-thorn (Lycium horridum) in the south-western part of 
the district are at the present time a physiognomic feature of the 
landscape. 
So little effect has that apparently important natural obstacle, 
Cook Strait, had upon the wandering of plants that no line of 
sufficient importance can be drawn to separate the southern North 
Island flora, and even vegetation, from that of the neighbourhood 
of the Marlborough Sounds and some portions of northern Nelson. 
Indeed, the true South Island flora does not begin, so far as the 
neighbourhood of the coast is concerned, until about latitude 42° 8. 
is crossed. Thus the followmg common North Island species extend 
to the South Island, some reaching as far as Greymouth, or even 
Banks Peninsula: The nikau-palm (Rhopalostylis sapida), the rewa- 
rewa (Knightia excelsa), the pukatea (Laurelia novae-zelandiae), the 
tawa (Beilschmiedia tawa), the epiphytic Pzttosporum cornifolium, 
the kohekohe (Dysoxylum spectabile), the wharangi (Melicope ternatc), 
the karaka (Corynocarpus laevigata), the titoki (Alectryon excelsum), 
the northern rata (Metrosideros robusta), the maire (Eugenia mare), 
the toro (Rapanea salicina), three species of olive (Olea Cunninghamii, 
O. lanceolata, and O. montana), the hangehange (Geniostoma ligustii- 
folium), the kanono (Coprosma grandifolia), two species of Alseuosmia 
(A. macrophylla and A. quercifolia), and the tauhinu (Cassinia lepto- 
phylla. . 
There are a number of plants which are found only in the 
Ruahine-Cook Botanical District, but they are of restricted distri- 
bution, while many of them are confined to the Tararua Mountains 
