EQUISETUM. 257 



minatcJ fin inch or two above the upper sheath, by cone- 

 like heads, rather more than an inch long, tapering some- 

 what above and below, and terminating in a blunt point. 

 The peltate thecoe-bearing scales, which are very nume- 

 rous, often exceeding a couple of hundred, are arranged in 

 whorls around the axis of the cone, as is the case generally 

 in this family. At a right angle with their margin are 

 ranged the spore-cases, four to seven in number ; they are 

 oblong, membranous, parallel, white cells, bursting finally 

 into two longitudinal valves, and discharging an abund- 

 ance of very minute globular spores, of a beautiful blue- 

 green colour. 



The barren stems are either erect or decumbent, and 

 from one to two feet or more in height ; they are often 

 branched from the bottom to the top, but sometimes only 

 the central and upper parts are branched. They spring 

 up after the fertile stems have withered, and are of a 

 pale-green colour ; at first crowded with short appressed 

 branches, which, by degrees, become elongated, and assume 

 a spreading or somewhat drooping position, sometimes 

 becoming again branched. The main stem has from ten 

 to sixteen distinct shallow furrows, with corresponding 

 ridges, and is, as well as the branches, studded over with 



s 



