FERNS OP GREAT BRITAIN. 147 



When the fertile stem has attained maturity, it is, when 

 growing on soils suitable to it, about eight or ten inches 

 high, but it is more frequently about half that height. 

 It is hollow, succulent, pale brown, without furrows, 

 and divided at intervals into joints ; the length of the 

 spaces between the joints is very variable, the joints at 

 the lower part of the stem being usually closer together 

 than at the upper. The sheaths are yellowish at the 

 base, and have about ten dark brown or black slender 

 teeth, with very sharp points. The upper sheaths are 

 longer than the lower ones, and the black teeth are 

 often tipped with white, and have a white clear margin. 



The cone-like fructification is at the top of the stem, 

 and is about an inch long, tapering upwards, termi- 

 nating in a blunt point, and standing on a distinct foot- 

 stalk about half its length. It is of a pale, or sometimes 

 of a reddish brown colour. The capsules are attached to 

 round scales, and arranged in whorls around it. The 

 number of scales varies, but they are not so numerous 

 in this species as in some others. In May, when 

 the catkin is matured, and sheds its numerous fine 

 green spores, these, like the spores of other species, 

 are, by the aid of the microscope, seen to be surrounded 

 by delicate threads, which uncoil with such curious 

 movements, that when looking at them we can scarcely 

 persuade ourselves that the motion is purely mechanical, 

 and is not the result of animal life. The oblong cap- 

 sules, when ripe, open by two valves, and discharge their 

 powder-like spores or seeds. 



The barren frond of this Equisetum is a very diiferent 

 looking plant, and is handsomer than the fertile one. 



