XIII 



THE INFLUENCE OF ENVIRONMENT ON THE 



FORMS OF PLANTS 



BY GEORG KLEBS, Pn.D. 



Professor of Botany in the University of Heidelberg. 



THE dependence of plants on their environment became the object 

 of scientific research when the phenomena of life were first investi- 

 gated and physiology took its place as a special branch of science. 

 This occurred in the course of the eighteenth century as the result 

 of the pioneer work of Hales, Duhamel, Ingenhousz, Senebier and 

 others. In the nineteenth century, particularly in the second half, 

 physiology experienced an unprecedented development in that it 

 began to concern itself with the experimental study of nutrition 

 and growth, and with the phenomena associated with stimulus and 

 movement ; on the other hand, physiology neglected phenomena 

 connected with the production of form, a department of knowledge 

 which was the province of morphology, a purely descriptive science. 

 It was in the middle of the last century that the growth of com- 

 parative morphology and the study of phases of development reached 

 their highest point. 



The forms of plants appeared to be the expression of their in- 

 scrutable inner nature ; the stages passed through in the development 

 of the individual were regarded as the outcome of purely internal 

 and hidden laws. The feasibility of experimental inquiry seemed 

 therefore remote. Meanwhile, the recognition of the great im- 

 portance of such a causal morphology emerged from the researches 

 of the physiologists of that time, more especially from those of 

 Hoftneister 1 , and afterwards from the work of Sachs 2 . Hofmeister, 

 in speaking of this line of inquiry, described it as " the most pressing 

 and immediate aim of the investigator to discover to what extent 

 external forces acting on the organism are of importance in deter- 

 mining its form." This advance was the outcome of the influence of 



1 Hofmeister, Allyemeine Morphologie, Leipzig, 1868, p. 579. 



2 Sachs, Staff und Form der Pflanzenorgane, Vol. r. 1880 ; Vol. n. 1882. Gesammelte 

 Abhandlungen ilber PJlanzen-Physiologie, n. Leipzig, 1893. 



