SPIBOGYRA. 



POND SCUM. 



SPIROGYRA is a filamentous alga common in ponds, 

 ditches, or sluggish streams during the summer months, 

 usually floating on the surface or adhering lightly to some 

 support. It is often called "pond scum," "frog-spittle," 

 "brook-silk." The scientific name comes from the spiral 

 arrangement of the chlorophyll in the cells. The alga may 

 be collected late in the fall and kept in aquaria all winter, 

 usually in good condition. 



I. Morphology. 



1. General Characters. Note the color, texture, slippery 

 feeling. Do different masses show variations in these 

 respects ? To what extent ? 



2. Microscopic Characters. Mount a few filaments in 

 water and examine with low, and with high powers. 



(a) Shape of Filament. Is it simple or branched? Is 

 it of uniform size? Are there signs of roots? Is there a 

 root end or a tip to the filament? 



(6) Structure. Is the filament composed of cells? If 

 so are they of uniform size? Note any variations. How 

 are the cells united? Is a cell wall clearly distinguishable? 

 Is it of uniform thickness over all portions of the cell? Stain 

 the filament by running a drop of iodine under the cover 

 glass and note effects on all parts of the cell. Are there 

 indications of starch? 



