86 PRACTICAL BOTANY. 



to be found floating as a hollow sac-like net in still, fresh water in 

 summer. Observation with the naked eye will show obviously 

 the meshes of the network. 



Mount a small piece in water and examine under a low power : 

 the four- to six-angled meshes will be seen to be limited by as 

 many cells, which are of large size. Each cell contains numerous 

 nuclei. When a new network is to be formed, the protoplasm 

 of one of these cells divides simultaneously into 7,000 to 20,000, 

 which move about, within the original cell-wall, and finally 

 arrange themselves in a new network, which, on growing, is 

 liberated by rupture of the parent cell- wall. This process may 

 be observed in healthy specimens in the height of summer. 



The whole cycle of life is a complicated one, and is somewhat 

 difficult of observation. 



