f diversity of specific form. Here then we meet the difficulty
that diverse environments often shade into each other insensibly and
form a continuous series, whereas the Specific Forms of life which
are subject to them on the whole form a Discontinuous Series."
This difficulty is, however, not of fundamental importance as well
authenticated facts have been adduced showing that by alteration of the
environment discontinuous variations, such as alterations in the number
and form of members of a flower, may be produced. We can as yet no more
explain how this happens than we can explain the existence of continuous
variations. We can only assert that both kinds of variation arise
in response to quantitative alterations in external conditions. The
question as to which kind of variation is produced depends on the
greater or less degree of alteration; it is correlated with the state of
the particular cells at the moment.

In this short sketch it is only possible to deal superficially with a
small part of the subject. It has been clearly shown that in view of the
general dependence of development on the factors of the environment
a number of problems are ready for experimental treatment. One must,
however, not forget that the science of the physiology of form has not
progressed beyond its initial stages. Just now our first duty is to
demonstrate the dependence on external factors in as many forms of
plants as possible, in order to obtain a more thorough control of all
the different plant-forms. The problem is not only to produce at will
(and independently of their normal mode of life) forms which occur
in nature, but also to stimulate into operation potentialities which
necessarily lie dormant under the conditions which prevail in nature.
The constitution of a species is much richer in possibilities of
development than would appear to be the case under normal conditions. It
remains for man to stimulate into activity all the potentialities.

But the control of plant-form is only a preliminary step--the foundation
stones on which to erect a coherent scientific structure. We must
discover what are the internal processes in the cell produced by
external factors, which as a necessary consequence result in the
appearance of a definite form. We are here brought into contact with the
most obscure problem of life. Progress can only be made pari passu with
progress in physics and chemistry, and with the growth of our knowledge
of nutriti