THE PLANT GROUPS 125 



SUPPLEMENTARY STUDY 



Equisetum arvense 

 SPOROPHYTE 



1. Dimorphic character of the aerial stems. 



a. Compare aerial vegetative and reproductive shoots of 



Equisetum arvense as to body plan, lateral organs, and 

 color. What is the apparent advantage of this division 

 of labor in aerial stems ? Do the reproductive and the 

 vegetative shoots grow at the same time of the year ? 

 Which has the longer life ? 



b. Construct a diagram to show the relations of the under- 



ground and the dimorphic aerial portions of Equisetum 

 arvense. Label parts correctly. 



2. Structure and reproduction. 



a. Structure. Cut thin sections across the stems of Equi- 



setum arvense. Mount and study with a low power. 



(1) Locate the main tissue layers : namely, epidermal, skele- 



tal (or supporting), vascular (or conducting), and stor- 

 age tissues. How does the general arrangement of 

 tissues differ from that found in the fern ? Can you 

 relate the position of the various tissues to their use, 

 or function, in the plant body, for example, the 

 skeletal and the green tissue ? Why are both of 

 these tissues placed on the outside of the stem ? Why 

 is the vascular tissue so small in amount ? What are 

 the advantages of the large intercellular spaces ? 



(2) Make an outline drawing (no cells) of your section 



illustrating the position of the various tissues. 



(3) Summarize the adaptive features of the structure of 



the stem. 



b. Asexual reproduction. 



(1) Compare the arrangement of the parts of the stro- 

 bilus of Equisetum arvense with that of the species 

 examined above as to plan and arrangement of parts. 



