EXPERIMENTAL MORPHOLOGY 7 
of morphological science will value the results already obtained from the 
application of experiment to the problems of plant-form. But it is 
necessary at the same time to recognise that the two phases of the 
study, the experimental and the speculative, are not antithetic to one 
another, but mutually dependent: the one can never supersede the other. 
The full problem of Morphology is not merely to see how plants behave 
to external circumstances ow—and this is all that experimental morphology 
can ever tell us-—but to explain, in the light of their behaviour now, how 
in the past they came to be such as we now see them. To this end the 
experimental morphology of to-day will serve as a most valuable guide, 
and even a check to any more speculative method, by limiting its 
exuberances within the lines of physiological probability. But present-day 
experiment can never do without theory in questions of descent. 
Experiment by itself cannot reconstruct history; for it is impossible to 
rearrange for purposes of experiment all the conditions, such as light, 
moisture, temperature, and seasonal change, on the exact footing of an 
earlier evolutionary period. And even if this were done, are we sure that 
the subjects of experiment themselves are really the same? There remains 
the factor of hereditary character: there is also the question as to the 
circumstances of competition which cannot possibly be put back to the 
exact position in which they once were. Consequently there must always 
be a margin of uncertainty whether a reaction observed under experiment 
to-day would be the exact reaction of a past age. So far, then, from 
experiment competing with, or superseding speculation in Morphology, it 
can only act as a potent stimulus to fresh speculation, whenever the 
attempt is made to elucidate the problem of descent. It will be only 
those who minimise the conservative influences of heredity, or, it may be, 
relegate questions of descent to the background of their minds, who will 
be satisfied by the exercise of the experimental method of morphological 
enquiry, apart from speculation. 
The relations of Morphology and Physiology have been variously 
recognised in the course of development of the science. In the earlier 
periods the two points of view rarely overlapped. Even Sachs, the great 
pioneer of modern experimental physiology, kept the two branches distinct 
in his . text-book, recognising the ‘ Difference between Members and 
Organs.” But later, in his lectures, he brought them more closely 
together, and habitually regarded morphological facts in their physiological 
aspect. This is indeed the natural position for any adherent of Evolution: 
and it has been concisely said that morphology deals with the stereotyped 
results of physiology. Such a statement may, however, be criticised as 
assuming too much, in that it accords all initiative in, and determination 
of form, as well as its selection and perpetuation, ‘to the influence of 
circumstance and function. A more apposite summing up of the relations 
of the two branches of Biological science has lately been given by Goebel} 
1+* Die Grundprobleme der heutigen Pflanzenmorphologie,” Biol. Centrbi., Bd. xxv., No.3. 
