CHAPTER V 



PLANT-CELLS ; SOME FUNCTIONS OF CELLS IN THE ROOT 



57. Structure of a Plant-Cell. — Plants are made up of 

 elementary organs called cells. These are small (usually 

 microscopic) objects of man}- diif erent shapes and subserve 

 various purposes in the life of the plant. The simplest 

 plants of all consist of but a single cell, which may have any 

 one of a great variety of shapes, but is often nearly spher- 

 ical. The higher plants, such as all the flowering plants, 

 consist of hundreds of thousands or millions of cells each, 

 and the total number m a large tree is inconceivablj' great. 



A single cell taken from the tip of a J j ^._^ ^ 

 growing shoot of any of 

 the higher plants, when 

 much magnified, is seen 

 to consist of a cell-wall 

 (»', Fig. 20) filled with a 

 more or less lic|uid sub- 



stance known as proto- j,^^ ^O. Twt rapidly Growing Cells (Doth 



plasm . A large part of greatly magnified, A twice as much as B). 



the bulk of this proto- ^ is a very young cell in wliieh the proto- 

 1 ■ i „ jr „ plasm does not as vet show vacuoles, i? 



plasm consists 01 a f ,, ... ■ , , 



r IS older, with several vacuoles ; )i, nucleus ; 



roundish object «, called nc, nucleolus; cy, protoplasm or cyto- 

 the nucleus, and inside P'^^-^^^ f, vacuoles; ^, cell-wall. 



this is a more opaque body nc, called the nucleolus. As 

 the cell grows the protoplasm is soon found to separate 



43 



n w 



