EQUISETUM. 233 



duce the fructification, and those which are barren, do not 

 differ in any other respect, and are, therefore, said to be 

 similar ; and in which, also, the stems are almost branchless, 

 the branching being mostly confined to the production of 

 one or two erect lateral stems from near the base, and this 

 lateral branching is by no means common. Sometimes, 

 indeed, the upper part of the stem is also sparingly 

 branched, but the branches are produced singly from the 

 whorls ; in very luxuriant plants, the branches are now and 

 then themselves branched upon a similar plan. 



Like the other species, this has a branching underground 

 creeping stem, which is black, and produces whorls of 

 branched fibrous roots from its joints. The above-ground 

 stems are slender, and erect in their mode of growth ; from 

 two to three or four feet high ; deeply furrowed, with a 

 double row of elevated points along the ridges, which are 

 usually from eight to twelve, but sometimes fourteen in 

 number. The sheaths are close, cylindrical, and striated 

 like the stem, terminating in a number of teeth equalling 

 the striae ; these teeth are long, slender, awl-shaped, black 

 with pale membranous margins, and usually, but not al- 

 ways, persistent. The sheaths are, for the most part, 

 entirely black, but here and there they occur with a narrow 



