442 PRACTICAL BOTANY 



CONJUGATE 

 SPIROGYRA 



1. In summer there may frequently be found, in 

 stagnant or slowly-flowing waters, flocculent freely- 

 floating masses of a vivid green colour, and slimy to 

 the touch : 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 and base. 



Mount a few of them in water, and examine them 

 under a low power : note that the simple unbranched 

 filaments are partitioned 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 Zygnetna, and, as these Alga3 

 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, 



