10 COMPENDIUM OF GENERAL BOTANY. 



dial utricle sometimes ruptures during sudden artificially induced 

 plasmolysis. 



III. CELL-CONTENTS. 



Tedious microscopic examinations of the cell-contents aided by 

 staining methods have recently brought to light a series of facts 

 and form-relations. But so far no conclusions of considerable 

 importance have resulted therefrom. The partially compiled and 

 partially original communications of A. ZIMMERMANN ' are especially 

 suited to give a comprehensive view of the work done and our 

 present knowledge of the subject. The most important results of 

 the above-mentioned investigations were obtained by the study of 

 the nucleus and the amyloplastids (starch-builders). STRASBURGEK, 

 GUIGNAKD, HEUSEK, SCHMITZ, KLEBS, ZACHARIAS, HABERLANDT, and 

 others have made special studies of the nucleus, while SCHIMPER. 

 has devoted much attention to the amyloplastids. 



For the sake of clearness it is no doubt permissible to select 

 from a subsequent chapter a few statements concerning cell-forma- 

 tion before taking up the cell-inclusions. 



In general cells originate in two ways : by division and by free 

 cell-formation. In the first case the form of the mother-cell and 

 the position of the septum determines the form of the daughter- 

 cells. In the second case the daughter-cells are approximately 

 spherical and float freely within the contents of the mother-cell. 

 In both cases the cells grow after they have formed. Deposits may 

 be made in all parts of the cell-wall uniform surface growth or 

 only at one portion apical growth of cell. In the latter case the 

 cell will gradually become more and more elongated. 



A. LIVING INCLUSIONS OF THE CYTOPLASM. 



(a) Nucleus. 



1. The nucleus is a more dense plasmic structure and is usually 

 present in all cells, though it is difficult to prove its existence in the 

 fungi. Some very large cells, as for example of Caulerpa (an alga) 

 which are often a foot or more in length, contain many nuclei ; long 

 bast-cells contain several nuclei. The majority of cells, hence those 



1 Die Morphologic und Physiologic der Pflanzenzelle. Breslau, 1887. Beitrage 

 zur Morphologic und Physiologic der Pflanzeiizelle, I, II, III. Tubingen, 1890, 

 1891, 1893. 



