THE SCOURING-RUSHES. 3' 



iiitcrmcdiiiin, and on the other it intergradcs ahnost 

 imperceptibh' with the smaller variegated scouring-rush. 



Ill outward appearance the smooth scouring-rush is 

 much like Rquisetuiii hicinalc, though usually shorter 

 and slenderer and with less silex in the epidermis. 

 Well-developed specimens may reach the height of four 

 feet, but the average is probably less than twenty inches. 

 The exterior is comparatively smooth and has from ten 

 to thirt}' grooves. The sheaths are long, green, and 

 dilated upward like a funnel, this last characteristic 

 being one of its most distinguishing features. There 

 seems to be some question as to whether or not the 

 stems last through the winter. All its affinities are 

 with the evergreen species, and it has always been 

 called evergreen in the books, but Mr. Eaton, the 

 latest monographer of the American species, has stated 

 that the stems are annual, and that the species may 

 be distinguished from Eqtiisctitm Incviale by this single 

 peculiarity. Further observations on this point are 

 desirable. The present lack is no doubt due to the 

 fact that the species is rare in the Eastern States, where 

 most of the studies of Eqnisetiun have been made. 



The stems of the smooth scouring-rush usually grow 

 in tufts from the summit of the rootstock. They are 

 slender and usually unbranched, though the more robust 

 specimens may develop several ascending branches from 

 near the base, especially if the tip be injured. In this 

 it is the reverse of the common scouring rush, which, if 

 it branches at all, does so near the tip of the stem. In 

 colour the stems are pale green, and a cross-section shows 

 a large central cavity with medium-sized vallecular 

 canals, those under the carinse being either smaller or 

 absent. On the exterior the grooves are somewhat 



