PROBLEMS OF PLANT MORPHOLOGY 85 



answer, e. g., the question as to the arrangement of leaves through 

 the effect of mechanical factors, or to refer the form-relations of a 

 plant to the direct influences of gravity and light on the plant. It 

 soon became evident, however, that such involved problems are not 

 to be unraveled by such simple means, and this may well have re- 

 sulted in the suppression of interest in morphology. 



At this point phylogenetic morphology appeared to take on a new 

 lease of life. This, however, in natural science is connected, on the one 

 hand, with the appearance of a new, creative idea, and, on the other 

 hand, with the discovery of new methods. Now the theory of descent 

 has powerfully stimulated morphological research. But has it 

 brought to it, as, e. g., Strasburger has held, a new method, the phy- 

 logenetic? Alexander Braun has already properly answered this 

 question in the negative. 



Scott, also, has maintained that historical morphology (as regards 

 both living and fossil plants) is dependent upon comparative study, 

 that is, makes use of the same method as was in evidence before the 

 appearance of the theory of descent; indeed, the most important 

 homologies in the plant kingdom became known through Hofmeister 

 at a time when the idea of descent was far from that general accepta- 

 tion which it at first gained through the life-work of Darwin. 



The method has then from first to last remained the same: the 

 most comprehensive comparison not only of mature forms, but 

 also their development. A special " phylogenetic method" there is 

 not, but only a phylogenetic conception of morphological problems. 

 These are, however, just as at first was the case with idealistic 

 morphology, purely formal. Modern morphology in my sense, how- 

 ever, differs from the older in this, that it goes beyond the method 

 of mere comparison. It allows the setting up of genetic trees to 

 rest for the while, since, with our present knowledge, this meets 

 with insuperable difficulties, and has brought almost as much disap- 

 pointment as the idealistic morphology. For just this reason, namely, 

 because we are persuaded that no other forces have been at work 

 during the phylogenetic history than those which now control the 

 development of each particular organism, do we wish, first of all, 

 more exactly to learn what these are. We are concerned not alone 

 with the determination of the single successive stages of devel- 

 opment. These must, of course, be followed, but in addition we 

 should follow all phenomena which may be got at by our means of 

 observation, whether directly, by the microscope, or by chemical 

 anatysis. We may, therefore, say: The basal problem of the pre- 

 sent-day morphology is not phylogenetic development, but devel- 

 opment in general. We must, therefore, take our departure from 

 the investigation of individual development (of ontogeny), for only 

 this lies before us complete and without any break, and further, 



