FORMATION OF CELLS. 



107 



Section S. KINDS OF THE CELL. 



The form and size of the cell vary greatly, the former 

 being spherical, elliptical, cylindrical, cubical, prismatic, 

 star-shaped, spindle-shaped, etc., and the latter being very 

 large as in Nitella, or very minute as in Bacteria. Longi- 

 tudinal rows of cells often become tulubar by the absorption 

 of their transverse walls. 



The cells, which are not much longer than they are 

 broad and have rounded or flattened surfaces, are said to be 

 Parenchymatous (Fig. Fia. 122. Fig. 123. 



122) ; those, which 

 are long and spindle- 

 shaped, Prosenchyma- 

 tous (Fig. 123); and 

 those, which are tubu- 

 lar from the absorp- 

 tion of their transverse 

 walls, Vascular (Fig. 

 115, 116 and 117). 

 The white central 

 portion of the stem 

 of the Yamabuki 

 (Kerria japonica) consists of parenchymatous cells ; the 

 hemp-fibres consist of prosenchymatous cells ; and the small 

 canals in the wood of the Kiri of vascular cells. 



Parenchymatous Cells. 

 Prosenchymatous Cells. 

 Vascular cells. 



: ( 



Fig. 122. — Parenchyma from the stem of 

 the Yamabuki (Kerria japonica). 



Fig. 123. — Prosenchyma from the stem of 

 the Hosenkwa. 



Kinds of cells 



Section 4. FORMATION OF CELLS. 

 The formation of cells takes place in different ways; 

 cells may be divided into two parts by the formation 

 of new transverse walls, each half becoming a new 



