SPIROG YRA. 



119 



Synopsis. 



Vegetative stage ; single unbranched threads, composed of 



cylindrical cells end to end. 

 Cells all alike. 



Grows by division and elongation of all the cells. 

 Spirogyra. -j Sexual stage ; conjugation of like cells. 



Receiving and supplying cells, not differentiated. 

 Result of conjugation, a zy go spore. 

 The zygospore after a period of rest produces the spirogyra 



thread again. 



Material. Spirogyra in conjugation, showing different stages, as well as 

 the zygospores. The material may be collected fresh, or it may be preserved 

 in 2% formalin collected in advance or purchased from supply companies. 

 Microscope, etc. 



