468 PROCEEDINGS OF SECTION D, 
a district, so that the geologist and botanist may mutually help 
one another to a considerable extent. The botanist, by indicating 
the limits within which certain plants are found, may assist the 
geologist in drawing the lines between different formations, if it 
can be shown that the plants in question affect particular classes 
of rocks. The geologist, on the other hand, can point out to the 
botanist the different characters of the rocks at various places, and 
thus help to explain the reason for what had previously only been 
observed. . 
To obtain, however, such a critical acquaintance with the flora 
of a district as to enable one to speak with confidence as to the 
limits within which particular species of plants are found requires 
a thorough knowledge of the country, and such as can hardly be 
obtained without a continuous residence for several years within 
the district. If followed up systematically, the results are, never- 
theless, likely to be both interesting and useful, and it is as a 
slight contribution to the study of local floras in connection with 
geology that these notes, relating to a particular district of New 
South Wales, are written. 
Before dealing with the plants of the Bathurst district, and 
their distribution within the same, it will be well to consider 
briefly what we may expect to find out about them. It is pro- 
verbially difficult to prove a negative; and the mere fact that a 
species of plant, well-known at one place, which we may call A, 
has not been recorded from another, B, does not prove that it may 
not be found at B subsequently. Seasons vary, and a plant may 
be common one year and very rare the next. Again, many plants 
have only a short period of flowering, and unless seen at that 
time are very liable to be overlooked or confounded with other 
species. Considerations such as these inculcate caution in arriving 
at decisions. Nevertheless, if, after working for some years, one 
finds that certain plants are almost always obtainable at one place, 
while on a different class of rock in the neighbourhood they have 
never been found, one may reasonably say that they are absent 
from the latter. Moreover, the occurrence of one or two isolated 
specimens at B would not entitle us to class it with A as a 
favourable locality for the plant. Knowing how widely seeds 
may be diffused, it could hardly be expected that a plant would 
not occasionally spring up in an unfavourable locality, but if it 
failed to maintain a footing it would be good evidence that the 
soil and surroundings were not sufficiently favourable to enable it 
to succeed in the battle of life. As an illustration of what is 
meant, the case of the well-known Cornish heath, Hrica vagans, 
may be cited. This plant has a very limited range in England, 
being almost confined to the Serpentine in the neighbourhood of 
Lizard Point. It is said to occur occasionally on Devonian rocks 
in Cornwall, but is not common there, so that, if found growing 
