0. EQUISETINE^S. 



EQUISETUM ARVENSE (The Common Horse- 

 Tail). 



THE SPOROPHORE. 



The Vegetative Organs. 



I. Observe with the naked eye the following external 

 characters in specimens of E. arvense which have 

 been carefully dug up. N.B. The root-stock being a 

 creeping one, and underground, it cannot be removed 

 from the soil without injury by merely pulling it up : 

 the specimens should be carefully dug up, so that the 

 several parts may be seen in their natural position 

 relatively to one another. 



1. The external conformation of the Axial struc- 

 tures or stems is the same whether they be creeping and 

 underground, or erect and aerial : they consist of more 

 or less elongated joints or Internodes, marked off 

 from one another by Nodes, which may be recognised 

 as the points of insertion of 



2. The Leaf-sheaths, each of which surrounds the 

 base of the interned e next above it, and splits at its 

 upper limit into Teeth, the number of which varies on 

 different axes. 



3. The internodes are marked by projecting longi- 

 tudinal Ridges, which may be traced upwards into the 



