146 FERNS OP GREAT BRITAIN, 



a necklace, and connected together by a minute chain of 

 particles. 



The Horsetails are readily distinguished ty their leaf- 

 less stems and the hollow angular channelled branches 

 which are in most cases whorled around them. The 

 different species are not, however, always very readily 

 discriminated, several of these being very similar, and 

 the structure of the sheaths around the joints, and the 

 ridges on the surface of the stems, often form the chief 

 features of their distinction. 



The Corn-field Horsetail is not, like most of the 

 species, peculiar to marshy .soils, but springs up every- 

 where, and is not only an annoyance to the farmer, who 

 finds it difficult of eradication from his corn or pasture 

 lands, but is also often a troublesome intruder into the 

 garden. Most of us have amused ourselves in child- 

 hood by giving a sudden pull to the stem or branch, and 

 thus separating it into small portions, leaving the sheath 

 in which each portion was enveloped disclosed to view, 

 and needing no microscope by which to discover its 

 little sharp membranous teeth. This species has a long 

 creeping root-stem, which is hollow, very much branched, 

 and jointed like the stem which rises above the ground ; 

 and it throws out at each joint a whorl of tough fibrous 

 roots. It has two kinds of fronds, the one fertile, and 

 without branches ; the other barren, and siirrounded by 

 the green whorls of rigid branches. 



The fertile stem rises above ground in March, and is 

 matured by April or May, at which season the barren 

 stems may often be seen lately emerged from the earth, 

 arrayed in the most delicate green colour, and very brittle. 



