INTRODUCTION. MORPHOLOGY AND ORGANOGRAPHY 5 



conveyed in these words, and the book which I wrote some sixteen years 

 ago was likewise designedly entitled ' The Comparative History of Develop- 

 ment of the Organs of Plants 1 .' In the following pages the organs of 

 plants are considered as being what they really are, organs or agents 

 of work, but I have not gone into the details of their functions, I have 

 only indicated in a general way the interdependence of form and function. 



The first question to which we have to find f an answer is: How 

 came it that the functions of organs were entirely divorced from morpho- 

 logy ? It is, and rightly so, one of the fundamental declarations of this 

 study that the function of an organ tells nothing about its ' morphological 

 significance,' or, in other words, the same function may be performed 

 by organs of very different morphological value ; ' homologous ' organs 

 must be distinguished from 'analogous' ones 2 . The tendrils of the vine 

 and of the passion-flower, for example, are shoot-axes whose leaves are 

 entirely or almost entirely suppressed ; but the tendrils of the Leguminosae 

 and of other plants, although like in form and function to those of the 

 vine and passion-flower, are transformed leaves ; the tendrils in the two 

 cases are analogous, they are not homologous. 



This knowledge is one of the weightiest acquisitions of morphology, 

 but at the same time it has been the cause of an incorrect generalization. 

 Because organs of like morphological significance may take on different 

 functions, the functions which they perform have been considered as of 

 subordinate importance, and therefore of no moment in the determination 

 of the characters of the organs ; hence it has been concluded that they 

 must be entirely neglected in the grouping of the different members of 

 plants in general categories. 



This conclusion is erroneous, as will be briefly explained hereafter. If 

 has led to an untenable position, especially in that fundamental problem 

 of morphology which from the time of Goethe has been styled the 

 ' Doctrine of Metamorphosis.' By this we understand the fact, that mani- 

 fold as are the organs of plants, they can be referred back to a few 

 ' fundamental forms ' through whose ' transformation ' the many and different 

 members of the plant-body have arisen. 



When we inquire how these primary forms and their transformations 

 have been represented to us. we meet with different conceptions on the part 

 of those authors who have taken pains to reflect upon the idea with which 

 they dealt. In the idealistic morphology, as it was expounded by Goethe, 

 A. Braun, and Hanstein. the doctrine of metamorphosis concerned itself 



1 Vergleichencle Entwicklnngsgeschichte der Pflanzenorgane, forming vol. iii. pt. i of Schenk's 

 Handbuch der Botanik. 



2 See afterwards on pages 18, 19. 



