140 LABORATORY AND FIELD EXERCISES 



b. Sporangia, Are the inicrosporangia abaxial or adaxial ? 



How many sporangia are there on a sporophyll ? 

 Determine the mode of dehiscence in mature spo- 

 rangia. Is the abaxial position an advantage in the 

 dissemination of spores ? Note the growth in length 

 of the internodes of the strobilus when the micro- 

 spores are ready for dissemination. 



c. Microspores. Study the structure of the microspores. 



How is it adapted to dissemination ? 



d. Drawings. Draw an abaxial view of a microsporophyll 



with its sporangia. Draw a microspore. 

 3. Pollination, fertilization, and carpotropic movements. If 

 material is available, study young pine and spruce 

 cones at the pollination stage. 



a. Pollination. What is the position of the strobilus at this 



stage ? What is the position of the sporophylls ? 



b. Fertilization. Compare the size and position of the 



strobili at pollination with that of similar strobili 

 at the time of fertilization and seed-shedding. Note 

 the changes in position of the strobili due to carpo- 

 tropic movements after pollination is effected. Com- 

 pare the pine and the spruce in these respects. 



c. Make outline sketches to illustrate changes in the size 



and position of pine or spruce strobili at the polli- 

 nation, fertilization, and fruiting stages. 



GAMETOPIIYTES 



1. Male gametophyte. Study the structure of the microspore 



and of the male gametophyte from prepared slides. 

 a. TJie microspore. How does the microspore differ in 

 structure from an ordinary cell ? Note the charac- 

 ter of the cell wall, nucleus, and cytoplasm. Draw 

 a microspore in section. 



