DEVELOPMENT OF PLANT PHYSIOLOGY 107 



which were at that time, as they still are, of great significance to 

 the systematist. Thus anatomy gained entrance into botany in the 

 beginning of the previous century, while the botanists of that time 

 yet saw something strange in the physical and chemical conception 

 of plants. Men such as Hedwig, Treviranus, Link, Meyen, and others, 

 who belonged to the ascendant school of botanists, went into plant 

 anatomy. The anatomical point of view must have led them to the 

 question of the functional significance of cells, vessels, and tissues, 

 and thus was developed, from the morphological side, the idea of 

 physiological study of the plant body, just as earlier the physiological 

 and the chemical methods had led to the same goal. 



It was the plant anatomist, then, who made physiology at home 

 among the botanists, especially in the German countries. The 

 works on plant anatomy of Treviranus, Meyen, and others, which 

 appeared during thirty years of the last century, give us evidences 

 of the spirit of the teachings of that time on the life of plants. The 

 independent observations and conceptions which are to be found in 

 these works bore a one-sided morphological stamp; and all that 

 dealt with the changes of force and materials in the plant had, on 

 the other hand, the character of compilation, in which the unma- 

 tured ideas of agriculturists were accorded a larger place than the 

 researches of the above-mentioned physiologists, who had already 

 departed the field of action. 



The whole of the botany of that time, as it was carried on in Ger- 

 many, had a one-sided morphological character. Under such cir- 

 cumstances, plant physiology could not flourish. This one-sided- 

 ness gave to botany, especially in Germany, its specific stamp, and 

 even such men as H. von Mohl could not escape the influence of their 

 time, although his clear intellect made better use of the literary 

 inheritance of plant physiology than did his colleagues. His mind, 

 better adapted for the study of nature, led him to question into the 

 field of experiment, in which he started some fundamental lines of 

 work, as, e. g., the study of twining, and of the tendrils of plants. 

 But his strength always lay in anatomy. In even this, where 

 questioning led straight to experiment, he clung as a rule to mor- 

 phology. An instructive and pertinent example is his relation to 

 the question of leaf-fall. The history of plant physiology and the 

 influence of other studies upon it are reflected so clearly in this 

 problem that I may be permitted a few moments to follow its devel- 

 opment. 



The physiologists of the earlier epoch had a purely mechanical 

 conception of this phenomenon. They held that leaves dried up 

 at their death, and that their stiffened forms were broken from the 

 twigs by the autumn winds. It was later held that the buds which 

 developed in the axils of leaves enter between them and the stem like 



