CHAPTER XXVII. 



HORSETAILS. 



379. Among the relatives of the ferns are the 

 horsetails, so called because of the supposed resem- 

 blance of the branched stems of some of the species 

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

 shown in fig. 239. They do not bear the least re- 

 semblance to the ferns which we have been study- 

 ing. But then relationship in plants does not depend 

 on mere resemblance of outward form, or of the promi- 

 nent part of the plant. 



380. The field equisetum. Fertile shoots. Fig. 

 2 33 represents the common horsetail (Equisetum ar- 

 vense). It grows in moist sandy or gravelly places, 

 and the fruiting portion of the plant (for this species 

 is dimorphic), that is the portion which bears the 

 spores, appears above the ground early in the spring. 

 It is one of the first things to peep out of the recently 

 frozen ground. This fertile shoot of the plant does 

 not form its growth this early in the spring. Its 

 development takes place under the ground in the 

 autumn, so that with the advent of spring it pushes 

 up without delay. This shoot is from 10 to 20 

 cm high, and at quite regular intervals there are 

 slight enlargements, the nodes of the stem. The 

 cylindrical portions between the nodes are the 

 internodes. If we examine the region of the inter- 

 nodes carefully we note that there are thin mem- j 

 branous scales, more or less triangular in outline, and 

 connected at their bases into a ring around the stem. 



187 



