124 LABORATORY AND FIELD EXERCISES 



the leaves on the main axis, thus following the 

 general body plan ? Is the strobilus placed in the 

 right position on the shoot for spore dissemination? 



2. Adjustments to the environment. Are there the same 



responses to environmental forces by tropisms in Equi- 

 setum as in ferns ? Be able to explain the relation 

 between the responses of the various organs and the 

 functions which they perform. 



3. Drawings. Make an accurate drawing of the Equisetum 



plant studied, to indicate the subdivisions and plan of 

 the plant body. Indicate by proper terms the responses 

 and adjustments of the various organs to environ- 

 mental forces. 



4. Analysis. Analyse one or more species of Equisetum and 



record analyses under family, genus, and species, as 

 in ferns. 



5. Habitat and habit. 



a. What is the usual habitat of the equiseta ? Are there 

 variations in habitat ? Determine these points by 

 field studies and by reference to texts and analytical 

 keys. Does the habitat of species growing in ponds 

 or lakes correspond to the form and structure of 

 these species ? How can you explain the evident 

 discrepancy between habitat and habit in these cases ? 



6. Seasonal history. Are equiseta annuals, biennials, or 



perennials ? herbaceous or woody plants ? In what 

 form do they pass the winter ? How do they differ 

 from ferns in these respects ? 



7. Summary. 



a. Summarize the distinctive characteristics of equiseta 



which differentiate them from true ferns. 



b. Explain the apparent discrepancy between habitat and 



habit in species growing in water. 



