226 THE PRESIDENTIAL ADDRESS DELIVERED
question of flower-producing conditions is one of supreme im-
portance to Essex fruit-growers. In such a field of meteoro-
logical and phenological work the humblest member of the
scientific community can take part, and I feel convinced there
are many members of the Club who would willingly work in this'
field, if the Club gave its benediction.
My other plea is in favour of the greater recognition by a
society of naturalists of the utilitarian or economic side of invest-
igations in natural science. The note of the scientific work of this
Club, as of other learned societies in this country, is "knowledge
for its own sake," and little advance in scientific knowledge
is ever made unless this be the guiding principle of the workers.
But I seem to see a propensity among naturalists to avoid
observations which may have an economic value. We go
fungus gathering in Epping Forest, but meanwhile gooseberry
bushes are being destroyed by a fungus which very few of us
have even learnt to recognise. We are charmed with the variations
in some entomological rarity, and meanwhile thousands of
black currant bushes at Burnham-on-Crouch are destroyed by
a mite whose life history would well have repaid further study.
At the Walthamstow reservoirs Mr. Scourfield gave us an
example of the aid which the naturalist can give to the water
engineer, shewing that the purification of water is partly due
to bacteria-devouring organisms, which form a sort of living
felt attached to the filtering medium. Of far-reaching significance
are the facts which have recently come to light upon the work
of similar organisms in destroying the putrefying and nitrifying
bacteria in the soil, and thus limiting fertility, so that any means
of destroying these organisms without destroying the spores
of bacteria (e.g. heating the soil, diving the soil, or applying
various chemicals) enormously increases its fertility. The micro-
scopists now tell us of some thirty bacteria-devouring organisms
(leucocytes, protozoa, etc.) in the soil, but it is not to them: that
we can credit the profound influence of this discovery on agri-
cultural science, but to an agricultural chemist, Dr. E. J. Russell,
who by an arduous series of investigations, first excluded all
chemical hypotheses to account for the observed effects of
heating soil on the subsequent crops grown in it.
And it is not only for the sake of the economic well-being
of agriculture that I plead, but also for the sake of societies of