170 



THALLOPHYTES 



The filamentous forms are composed of single rows of cells, 

 each cell capable of sub-division, and if separated from the 

 others, of producing a new plant. The very common Spirogyra 

 (Fig. 109) is an excellent type for study. The cells are cylin- 

 drical in shape and attached end-to-end. Each cell contains an 

 imier lining of protoplasm and numerous cross strands of the 

 same material ; also a nucleus which may be located in any 

 part of the cell but usually in the centre. The protoplasm and 

 nucleus are transparent and cannot be seen readily without the 



Fio. 109. — Spriogyra: 

 Fig. 110.— CEdogoniur 



single cell showing chromatophore and nucleus; b, two plante 



showing sexual reproduction, 

 a, plant showing non-sexual cells; b, plant showing oogonium 

 and antheridium. 



use of an artificial stain. The spaces between the strands of 

 protoplasm are known as vacuoles and are filled with water. 

 Embedded in this protoplasm will be readily seen the spiral 

 chrornatophores or chloroplasts containing the chlorophyll. Scat- 

 tered along this chlorophyll will be seen the round shining 

 pyrenoids which are supposed to be the centres for food forma- 

 tion or photosynthesis. The cell of the spirogyra may be looked 

 upon as a typical plant cell in which all the functions of plant 

 life are performed. 



Spirogyra. — Tf we examine a great many plants of spiro- 

 gyra. we will probably find some specimens which are attached 



