EQUISETALES (HORSETAILS) 



435 



Some Plants Resembling True Ferns. Some plants which 

 resemble the True Ferns, although they belong to another group, 

 are the Botrychiums or Moonworts that are common in the woods 

 (Fig. 388). They have an underground stem which sends up 

 leaves that have a finely divided vegetative portion and a spore- 

 bearing portion that much resembles clusters of small grapes. 



FIG. 389. A section through the tuber-like gametophyte of Botrychium, 

 showing one archegonium and a number of antheridia in the upper surface. 

 X about 10. 



It is, however, in their gametophyte generation that they differ 

 most from True Ferns. Their gametophytes are tuberous sub- 

 terranean structures bearing the sex organs on the upper surface, 

 and associated with the gametophytes there is always an 

 endophytic Fungus (Fig. 389). 



Equisetales (Horsetails) 



In ancient times, as shown by their fossils in coal and other 

 kinds of rock, the Equisetales were very abundant, but the only 

 surviving group is the Horsetails. Their slender stems, often 

 called Joint Grass, are common in meadows, in moist places in 

 the woods and along roadsides. There are about 25 species of 

 Equisetum. There is Equisetum palustre common in swamps, 

 Equisetum pratense and Equisetum arvense common in meadows 

 and fields, and so on. Those growing in meadows and fields 

 are often troublesome weeds. They are widely distributed over 

 North America and also occur on other continents. They range 

 in height from a few inches to several feet. It is reported that 

 one form in the West Indies and Chili sometimes reaches a height 

 of 40 feet, but in our region 3 or 4 feet is a good height. The 

 Equisetums are also called Scouring Rushes because their stems 

 contain silica which is used in making scouring powders. 



