212 T'ransactions.— Botany. 
The influence of temperature, however, in producing a luxuriant plant-growth 
is of less importance than humidity, whether derived from the normal humid 
condition of the prevailing winds, or locally by the evaporation from swamp 
lands or the cover of bush. The amount of humidity present in the atmosphere 
differs much in different districts, and can be easily known without the aid of 
meteorological instruments by the greater or less abundance of those low forms 
of vegetable life—the lichen-fungi— whose minute forms often give a colouring 
to rocks and bark of trees. "They are seldom found where dry winds prevail, 
but often in great profusion on the coast line, and inland for several miles, and 
at altitudes on the hills where rain-clouds hang. The normal condition of the sea- 
winds at Wellington is humid, but for short periods cold arid winds accom panied 
by rain prevail whose blighting influence on some plants, especially those 
with membranaceous leaves, or tender introduced species, is almost destructive, 
and, but for the shelter of more robust species, many (such as Piper excelsum) 
would become extinct. This blighting influence of the sea-winds has been 
erroneously ascribed to the presence of salt carried from the ocean; but if 
this were the case every storm should produce the same blighting effect, 
whereas it occurs seldom more than once or twice in a year, and only for a 
few hours, 
For convenience the flora of Wellington will be arranged under five natural 
divisions : bush, open land, alpine, littoral, and marine. From the equability 
of the climate, the species of the first and second divisions are very uniformly 
distributed over their own areas up to 2,000 feet. It is presumed, therefore, 
that any artificial system of zones of altitudinal distribution in a district where 
the greatest altitudes are only 5,000 feet would fail in correctness, as it has 
been already shown that the selection of habitat by species within this limit is 
more influenced by soil than temperature. 
The geographical position of the timber trees is a subject of much 
importance in a commercial point of view. As the country is opened up by 
railroads it will be found that the species easiest reached differ in different 
districts, both in kind and value. The value of any timber being proportionate 
to its strength and durability for constructive or other works, these qualities 
again are entirely ruled by the kind of soil and the amount of exposure under 
which it is grown. For it is an erroneous idea that if once some particular 
kind of tree, such as totara, has produced durable timber, all totara will be 
durable ; for that which is grown on rich alluvial sheltered bottoms will, 
undoubtedly, be inferior in durability to that which is grown on exposed hill- 
ridges, the growth of the latter being much slower, producing a timber of 
greater specific gravity and containing more secreted oil. So, also, does soil 
and exposure influence the strength of those timbers which are selected for 
building purposes (such as rimu), where capacity to resist transverse strain is 
