50 GENERAL BIOLOGY. 



Sketch a complete cell with half of each adjacent 

 cell(X 5). 



Stain slightly with iodine and carefully re-examine 

 the cell-structures. 



Look again at the different structures of the cell 

 in preserved specimens stained with borax car- 

 mine* 

 I. Reproduction. 



Mount in water a group of filaments of conjugating 

 spirogyra. Examine with D 2. 



[There may be present several species of Spi- 

 rogyra differing in the number of the chro- 

 matophores. In addition to Spirogyra other 

 closely related forms may also be present, 

 asMesocarpus and Zygnema, differing chiefly 

 in the size of the filament and in the shape 

 of the chromatophore.] 



Search for a series of forms to show the differ- 

 ent stages in the process of conjugation. 



Observe the zygospores: large and oval. [Those 

 of Zygnema smaller and more rounded.] 



In perfect specimens each filament containing 

 zygospores is connected with a filament with 

 empty compartments. Find cells whose walls 

 have just begun to send out a projection from 



* To preserve Spirogyra, put it into a saturated aqueous solution 

 of picric acid for 12 hours. Wash for an equal length of time in 

 water. Stain for some hours in borax carmine. 



