THE PLAXT GROUPS 129 



c. Draw a portion of a Selaginella plant to illustrate the 

 above points. 



2. Asexual reproduction. 



a. Strobili. Do the species of Selaginella that you are 

 examining bear distinct strobili? What is the nature 

 of the sporophylls ? Do they resemble ordinary 

 leaves in form and color ? Why are they called 

 sporophylls ? 



I. Sporangia and spores. 



(1) Remove sporophylls from different parts of the stro- 



bilus and examine the sporangia. Are the sporangia 

 all alike in appearance and in the number of spores 

 which they bear ? Dissect spores from several spo- 

 rangia to determine this point. What do you find? 

 Have we studied any plants before which bore two 

 kinds of spores ? Do any particular portions of 

 the strobilus bear a particular kind of sporangium 

 and spore ? 



(2) Draw the two kinds of sporangia and sporophylls 



found in the strobili that you are examining. 

 Draw the two kinds of spores. Eead the text 

 on asexual reproduction of Selaginella and label 

 your figures correctly. 



(3) Study of sections. If sections of strobili of Sela- 



ginella are available, study the relations of the 

 microsporangia and megasporangia to the main 

 axis of the strobilus and to the sporophylls. 

 Observe the structure of the sporangia and 

 spores. Draw and label your figure. 



3. Life history. Study the text figures and discussions con- 



cerning the gametophytes, sex organs, and life history 

 of Selaginella. 



4. Distinctive characteristics. Summarize the new and dis- 



tinctive characters of Selaginella. 



