Equisetum (HORSETAIL) 



A. Classification: 



Division IV. Calamophyta. 

 Class II. Equisetineae. 

 Order. Equisetales. 

 Family. Equisetaceae. 

 Genus. Equisetum. 

 Species, (e.g.) arvense L. 



B. Habitat: 



i. The field horsetail (E. arvense), is common along 

 railway embankments, roadsides, and fields. It 

 apparently prefers north-facing slopes, and has a 

 great tendency to become weedy. 



C. Naked-eye Characters: 

 i. The Stem. 



(a) Using herbarium specimens or alcoholic material, 

 if fresh material is not available, observe the 

 underground stem (rhizome), and the upright 

 aerial branches. 



(b) Of the latter, observe two kinds: (i) non-green, 

 unbranch^d, bearing only scale-leaves, and 

 terminating in a prominent strobilus or cone; 

 (2) green and branched, also bearing scale- 

 leaves, but no cone. 



(c) Which kind of aerial branch appears first above 

 ground in the spring? What advantage may 

 this possess for the species? 



(d) Explain the physiological significance of the 

 green color of the non-reproductive branches. 



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