474 PROCEEDINGS OF SECTION D. 
towards classifying our rocks will have been made. There can be 
little doubt that the main cause determining the flora of the dis- 
trict, apart from climate, is the character of the soil, but it does 
not follow that an ordinary analysis of a soil will indicate its fitness 
for particular plants. An analysis, as a rule, only furnishes the 
percentage of acids and bases which are present in weighable 
quantities inanaveragesample. But there may be rarer elements 
present in small quantities, and these are not usually looked for, 
although they may be of importance to some plants. The ash of 
tobacco is said nearly always to contain lithium, so that this 
element must be widely diffused, but it is not likely to be looked 
for in an analysis, and the same is true of other elements, such as 
fluorine. Something has been done to trace the association of 
certain elements with particular species of plants, but, with few 
exceptions, very few definite results appear to have been obtained. 
Mr. 8. B. J. Skertchly has recently treated the subject of the, so- 
called, copper plant, Polycarpea spirostylis, F.v.M., which is said 
to accompany copper lodes, in his report (Geological Survey, 
Brisbane, 1897) on the Tin mines of Watsonville, Queensland, 
in which he also alludes to some literature in reference to 
similar cases. So far, the writer has not noticed anything of 
the kind, except the apparent abundance of Leucopogon virgatus 
in the neighbourhood of quartz reefs, which may be only a local 
peculiarity. 
Another point worthy of consideration in dealing with the 
distribution of plants, especially in relation to their abundance or 
scarcity in particular seasons, is the action of parasites, animal or 
vegetable. 
The parasites of cultivated plants have been carefully studied, 
although even with these it is not always easy to say why they 
are so much commoner in some seasons than in others. Much 
less attention has been bestowed on the parasites of wild plants, 
and yet they are equally interesting to the botanist. To take the 
case of a common weed; a few years ago the mallows, which are 
very common at the sides of roads and in small paddocks about 
Bathurst, were extensively attacked by a rust, Puccinia malva- 
cearum, which also attacked Hollyocks and other plants belonging 
to the same order, Malvacee. For several years the mallows 
appeared to be not nearlyso common. This year, 1897, they have 
been excessively abundant, but do not seem to be rusted. 
Another case noted by the writer is that of a Cassytha, pro- 
bably C. glabella. This parasite attacks several kinds of plant, 
but seems to be selective in the choice of its host. Last year, 1896, 
a small-leaved wattle, probably A. buwxifolia, was very abundant, 
as a shrubby plant, on the Silurian in early spring. Later hardly 
one was to been seen alive. Many had evidently been badly 
attacked by Cassytha, and may have been killed by it. A. diffusa, 
