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 now 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 l 

 " Die Grundprobleme der heutigen Pflanzenmorphologie," Biol. CentrbL, Bd. xxv., No. 3. 



