126 LABOKATOKY AND FIELD EXERCISES 



(2) Bisect a strobilus. What are the parts of a strobilus 



thus exposed ? Is the strobilus a modified shoot ? 

 Are there nodes, internodes, and lateral members, 

 as in the main central axis ? 



(3) Sporangiophores and sporangia. The sporangiophores 



are the shield-shaped lateral organs of the strobilus 

 which bear the sporangia. They are not true sporo- 

 phylls, or modified leaves. How many sporangia 

 are there on a single sporangiophore ? How are they 

 arranged ? What is the shape of a sporangium ? 

 Dissect sporangia out on a slide to determine this 

 point. Can you determine the mode of opening 

 in rather mature sporangia? Draw sporangia to 

 show the line of dehiscence. 



(4) Spores and elaters. Dissect spores out on a slide (let 



them dry if preserved material is used). Breathe 

 on them gently. Result ? Study the structure of 

 the spores. Draw them. See the text for a descrip- 

 tion of spore structure. Label your drawing. 

 3. Life history and relationships. Study the life history of 

 Equisetum in the text. 



a. Why are these plants classified with the ferns under the 



common group Pteridophyta ? 



b. In what respects are the ferns and equiseta alike in their 



life history ? Summarize your conclusions respecting 

 a and b in your notes. 



C. LYCOPODIALES (CLUB MOSSES) LYCOPODIUM 

 SPOROPHYTE 



1. The plan of the plant body. Compare with that of true 

 ferns and equiseta. Are there characters concerned 

 with the central axis or the lateral members (leaves, 

 roots, and branches) which distinguish lycopods from 

 the other Pteridopliyta already studied? 



