THE SCOURING-RUSHES. 



37 



weak that they often spread about in a half-recumbent 

 position. Externally they are marked with from four to 

 ten broad, rounded, or slightly two-angled ridges with 

 still broader hollows between. A cross-section shows the 

 central hollow to be about one third the total diameter, 

 the vallecular canals to be relatively large and trans- 

 versely oval, while the carinal canals are much smaller. 



The sheaths are of moderate length, slightly dilated 

 upward, and tipped with elongated, triangular, slender- 

 pointed teeth with white margins which may or may not 

 fall off at maturity. At the base of old stems the sheaths 

 are jet black ; higher up they are ash-colour with two 

 black girdles, one at the base and one on the margin ; 

 while near the apex and in 3'oung stems they may 

 be clear green with only a narrow blackish band 

 on the margin. The leaves are four-ridged, the 

 two middle ridges separated by a rather deep 

 groove, this latter being considered an impor- 

 tant point in identifying the species. The cat- 

 kins are slightly ovate, half an inch or under 

 in length, and tipped with a comparati\'ely large 

 point. After fruiting, the sporophylls often fall 

 from the axis of the cone, which may persist in 

 this condition for some time. 



The variegated scouring-rush is a lover of the 

 North, and inhabits a zone encircling the earth i^^„'/j"/°L 

 from about the 42d parallel of north latitude to ^''"■"'■'^"'""' 

 the Arctic Circle and beyond. In the southern part of 

 its American range it has been reported from all the 

 northern tier of States and from Illinois and Indiana. 

 It has often been reported from the Southwestern 

 .States, but it is likely that in such cases Equisctum 

 licvio;atiim ma\' have been mistaken for it. It grows in 



