78 LABORATORY AND FIELD EXERCISES 



b. The nucleus. Study the nucleus in stained material. 

 What is the form of the nucleus and where is it 

 located in the cell ? Is it connected with the pyre- 

 noids ? Study several cells with reference to these 

 points. Draw a Spirogyra cell to show the nucleus 

 in its proper position and in its connections with 

 the pyreuoids. Construct a transverse section of a 

 Spirogyra cell cut through the nucleus. Label all 

 parts correctly. See Fig. 118 of the text. 

 3. Reproduction. 



a. Conjugation of the filaments. 



(1) Study early conjugating plants with a low power. 



Observe the method of union of the filaments. 

 Do you find different stages in the formation of 

 protrusions from the cells and in the formation 

 of connecting tubes ? Observe whether the union 

 of the filaments affects the cytoplasm of the 

 uniting parent cells. 



(2) Draw stages representing the union and conjugation 



of the filaments in Spirogyra. 



b. Formation of the gametes. 



(1) Study plants in which gametes are forming. Ob- 



serve as many stages in gamete formation as 

 possible in the material at your disposal. Do you 

 find male gametes forming before the female 

 gametes in cells united by connecting tubes ? 

 What is the method of gamete formation ? What 

 is a gametangium ? Consult the text for the 

 meaning of this term. How does it differ from a 

 gamete ? What are the structural parts of each ? 



(2) Draw gametangia in which gametes are forming. 



Indicate as many stages in gamete formation as 

 you find. Label gametangia and gametes. 



