EQUISETTJM. 249 



becoming elevated on a short stalk. The scales are from 

 forty to fifty in number, and are of a pale brown colour, 

 bearing numerous whitish spore- cases. 



The branched fertile stems have their sheaths smaller 

 than the simple fertile ones, but larger than the barren ones. 

 Several of the uppermost joints produce whorls of branches, 

 and the stem is terminated by a cone of fructification. In 

 these cases, however, the number of branches is less than 

 that produced by the ordinary barren stems, and the cone is 

 smaller than those produced by the ordinary fertile stems. 

 In fact, the parts seem intermediate. 



The section of the stem of this species is very different 

 from that of any other, though having most resemblance to 

 those of JE. arvense and K sylvaticum. The exterior shows 

 a series of sharp ridges with angular furrows ; the central 

 cavity rather exceeds a third of the whole diameter; the 

 cylinder of the stem is then pierced by three circles of ca- 

 vities one of longish oblong openings opposite the furrows, 

 one of minute pores exterior to these and opposite the ridges, 

 and another of minute pores on their inner side also oppo- 

 site the ridges. 



Probably this species is tolerably plentiful in moist shady 

 woods, which are the situations it affects, but it has as yet 



