100 REPRESENTATIVE PLANTS 



What transparent substance might occupy the seemingly 

 unoccupied parts of the cell ? This seemingly unoccupied 

 space in the cell is in reality filled with cell liquid and is 

 often called the vacuole. 



End of filament. Examine the end of a filament, (Ip) or 

 (hj)). What is the shape of the end? Explain, if possible. 



Species of spirogyra. Examine different kinds of spiro- 

 gyra for varying numbers of chloroplasts. How many 

 kinds do you discover ? How do they compare with refer- 

 ence to size, color, or cell structures other than the chloro- 

 plasts ? Such differing kinds are called species. Spirogyra 

 is a,geniis name. The two names with the genus first, followed 

 by the species, constitute the scientific name. All plants 

 have such names in universal use. 



Reproduction. Conjugating spirogyra. If specimens are 

 given to you showing conjugation, look for the parallel fila- 

 ments, the short tubes (conjugating tubes) connecting adja- 

 cent cells; also any change in the cell contents. These 

 cells which are uniting by the connecting tube are called 

 gametes and the process shown is known as sexual reproduc- 

 tion, or the production by cell union of a spore (called by 

 various names, zygospore, zygote, and later, oospore). Plants 

 or cells (in plants consisting of single cells) thus uniting are 

 known as gametophytes. In spirogyra, although a filament 

 of many cells constitutes the plant body, in reality, each 

 cell of sucli a filament can exist independently. If you see 

 dark oval bodies in tlie cells, the other paired cells being 

 empty, they are the oospores, or reproductive cells, formed 

 by the union of the cell contents of the two connected cells. 

 If possible, note the various stages in the process. Read 

 about the purpose of these cells in the life history of 

 spirogyra. 



Drawings. Make the following drawings to show the 

 results of your observations : (1) a mass as it appears with 

 hand lens; (2) a filament of at least ten cells (?p) ; (3) a 



