n the physiological problems which occupied so much of his
later life. But inasmuch as he felt evolution to be his life's work, he
regarded himself as something of an idler in observing climbing plants,
insectivorous plants, orchids, etc. In this physiological work he was
to a large extent urged on by his passionate desire to understand the
machinery of all living things. But though it is true that he worked
at physiological problems in the naturalist's spirit of curiosity, yet
there was always present to him the bearing of his facts on the problem
of evolution. His interests, physiological and evolutionary, were indeed
so interwoven that they cannot be sharply separated. Thus his original
interest in the fertilisation of flowers was evolutionary. "I was
led" ("Life and Letters", I. page 90.), he says, "to attend to the
cross-fertilisation of flowers by the aid of insects, from having come
to the conclusion in my speculations on the origin of species, that
crossing played an important part in keeping specific forms constant."
In the same way the value of his experimental work on heterostyled
plants crystalised out in his mind into the conclusion that the product
of illegitimate unions are equivalent to hybrids--a conclusion of the
greatest interest from an evolutionary point of view. And again his work
"Cross and Self Fertilisation" may be condensed to a point of view
of great importance in reference to the meaning and origin of sexual
reproduction. (See Professor Goebel's article in the present volume.)

The whole of his physiological work may be looked at as an illustration
of the potency of his theory as an "instrument for the extension of the
realm of natural knowledge." (Huxley in Darwin's "Life and Letters." II.
page 204.)

His doctrine of natural selection gave, as is well known, an impulse
to the investigation of the use of organs--and thus created the great
school of what is known in Germany as Biology--a department of science
for which no English word exists except the rather vague term Natural
History. This was especially the case in floral biology, and it is
interesting to see with what hesitation he at first expressed the value
of his book on Orchids ("Life and Letters", III. page 254.), "It will
perhaps serve to illustrate how Natural History may be worked under the
belief of the modification of species" (1861). And in 1862 he speaks
(Loc. cit.) more definitely of the relation of his work to natural
selec