INTRODUCTION. 



The body of the plant is composed of parts with definite position, succession, 

 structure, and direction of growth. These we call its members '■, when we refer only 

 to their share in the structure. Investigation teaches us to recognise members of 

 different, and, in plants of complicated structure, numerous ranks. Roots and leafy 

 •shoots ; internodes, leaves, segments, and layers of meristem, masses of cells ; finally, 

 the single cell, which may again be separated into members. 



Each member, of whatever rank, is adapted according to its development to 

 definite physiological work. It becomes the instrument, or organ of this work. As 

 was the case with members, there may also be distingiyshed organs of different rank- 

 simpler, and gradually more complicated. According as an organ adapts itself to a 

 definite function, it attains properties of form and structure, which are definite, and 

 differ from those of other organs. 



The description and explanation of the collective phenoniena of form and struc- 

 ture constitute the task of morphology. According to the two points of view now put 

 -forward, we must distinguish between the morphology of members, and the morpho- 

 logy of organs. The former deals exclusively with the phenomena and laws, according 

 to which the organism is compounded of the members of different rank ; the morpho- 

 logy of organs with the properties of structure and form, by which the members 

 become organs, and with the distinction of organs of different rank, according to 

 those properties. Strictly speaking, the morphology of the organ presupposes a 

 knowledge of that of the member, since the origination of a member must precede 

 its evolution into an organ. As a matter of fact, a sharp separation of the two 

 disciplines can hardly be carried out, since both work with the same material, which 

 extends from the realm of the one to that of the other without any definite break. 



The subject of this book is a part of the morphology of the organs of Plants, 

 which is limited for convenience sake. According to the programme of the Hand- 

 book, of which it is a part, it should treat of ' the anatomy of the Vegetative Organs of 

 Vascular plants ;' it is occupied therefore only with the Phanerogams, and Pterido- 

 phyta, i. e. the Fern-like plants in the widest sense of the word. Further, it pre- 

 supposes such knowledge, gained from other sources, of the outward form of organs 

 of higher rank (a. g. foliage-shoots, roots, &c.) as can be acquired without anatomical 

 investigation, and treats only of their internal structure. Lastly, it is limited to the 



Sachs, Textbook, second English edition, p. 149. 

 B 



