CHAPTER VI 



PLANT CELLS 



cell wall 

 ■cytoplasm 



nucleus 



The Structure of Plant Cells. — The typical cell of the higher plants 

 is a tiny compartment enclosed by a tough elastic wall (Fig. lo). The 

 wall of cells consists of two major parts: (i) The middle lamella and (2) 



the primary wall (Kerr and Bailey, 

 1934). I'l walls of many plant cells a 

 third structural component, the sec- 

 ondary zvall, is also present. Although 

 some plant cells are known which do 

 not have a well defined cell wall, this 

 structure is so generally present in plant 

 cells as to be considered one of their 

 characteristic features. 



Lining the interior of the wall and 

 occupying more or less of the cell cavity 

 is the protoplasm. The protoplasm of 

 active cells is a transparent, slightly 

 viscous, granular material that lacks 

 CnloroplasT ai^y conspicuous structural background. 

 It is not homogeneous, however, and 

 contains a number of definite struc- 

 tures. One of these, the nucleus, is a 

 denser body which is more or less 

 spheroidal in shape and is separated 

 from the remaining protoplasm by a 

 definite membrane, the nuclear mem- 

 brane. Within the membrane sur- 

 rounding the nucleus are : ( i ) a clear 

 liquid known as the nuclear sap, (2) a 

 delicate network of denser material, the 

 reticulum, and (3) one or more small spherical masses of material known as 

 the nucleolus or nucleoli. 



All of the protoplasm outside of the nucleus of the cell constitutes the 



60 



vacuole 



Fig. 10. Perspective view of a 

 palisade cell from the leaf mesophyll. 



