HORSETAILS. 



1 77 



291. Sterile shoot of the common horsetail. — When the 

 spores are ripe they are soon scattered, and then the fertile 



Fig. 152. 

 Spore of equisetura 

 with elaters coiled up. 



Fig. 153- 

 Spore of equisetum with elaters un 

 coiled. 



shoot dies down. Soon afterward, or even 

 while some of the fertile shoots are still in 

 good condition, sterile shoots of the plant 

 begin to appear above the ground. One of 

 these is shown in fig. 154. This has a 

 much more slender stem and is provided 

 with numerous branches. If we examine 

 the stem of this shoot, and of the branches, 

 we shall see that the same kind of leaves are 

 present and that the markings on the stem 

 are similar. Since the leaves of the horsetail 

 are membranous and not green, the stem 

 is green in color, and here the process of 

 starch formation goes on. These green 

 shoots live for a great part of the season, 

 building up material which is carried down 

 into the underground stems, where it goes 

 to supply the forming fertile shoots in the 

 fall. On digging up some of these plants 

 we see that the underground stems are often 

 of great extent, and that both fertile and 

 sterile shoots - are attached to one 

 and the same. 



292. The scouring rush, or shave 

 grass. — Another common species of 

 horsetail in the Northern States grows 



Sterile 



Fig. 154- 

 plant of horsetail .(Equi- 

 setum arvense). 



