SPIROGYRA 223 



CONJUGATE 

 SPIROGYRA 



I. In summer, in stagnant or slowly-flowing waters, flocculent 

 freely-floating masses of a vivid green colour, and slimy to the 

 touch, may frequently be found : with the naked eye it may be 

 seen that the masses consist of coiled and tangled unbranched 

 filaments, in which there appears to be no distinction of apex 

 or base. 



Mount a few of them in water, and examine them under a low 

 power : note that the simple unbranched filaments are parti- 

 tioned off by transverse septa into a number of relatively short 

 cells. It will usually be obvious that the filaments are not all 

 alike, and two chief types will frequently be found present 



a. Those with two star-like green bodies in each cell : these 

 belong to the genus Zygnema, and, as these Algae are not so 

 well fitted for a detailed observation, they may be neglected. 



b. Others will be seen to have one or more spirally coiled 

 green bands in each cell : these belong to the genus Spirogyra. 



A superficial observation of specimens collected at the same 

 time and place will usually show that in different filaments 

 there is considerable variety in size, form of the cells, thickness 

 of the walls, and in the number and arrangement of the spirals : 

 according to these characters (together with those of the 

 zygospore) a large number of species of Spirogyra are distin- 

 guished. It will be found convenient to select for observation 

 specimens of the largest size, and with the coils of the green 

 spirals furthest apart. Examine such filaments in detail under 

 a high power, in the living state, mounted in water, and 

 observe 



