CHAPTER XXVIII. 



HORSETAILS (EQUISETINEyE). 

 (The field equisetum.) 



283. Equisetum is related to the ferns. Among the rela- 

 tives of the ferns are the horsetails, so called because of the 

 supposed resemblance of the branched stems of some of the 

 species to a horse's tail, as one might infer from the plant 

 shown in fig. 154. They do not bear the least resemblance to 

 the ferns which we have been studying. But then relationship 

 in plants does not depend on mere resemblance of outward form, 

 or of the prominent part of the plant. 



The field equisetum (Equisetum arvense) is a good one to 

 study. If desired another one may be used for comparison, the 

 scouring rush, or shave grass (E. hyemale). 



Exercise 55. 



THE FIELD EQUISETUM. 



284. Fertile shoots. The material should show the underground stem. 

 Note the underground stem, its branching, color ; the connection of the up- 

 right fertile shoot with it. Note the roots. What is the color of the fertile 

 shoot ? Is there much chlorophyll ? 



Observe the nodes (joints) of the stem, the membranous crown (leaves) 

 around each node, the character of the margin of this crown. Study the 

 internodes, note the marking into ridges and furrows. What is the relation 

 of the ridges and furrows of one node with those of each adjacent node ? 

 What is the relation of the points of the leaves with the ridges ? Sketch a 

 fertile shoot. 



285. The fruiting spike. The fruiting spike at the end of the shoot. 

 Observe the numerous disks which are also arranged in whorls. Tease off 



174 



