THE GENUS EQUISETUM IN NORTH AMERICA. 



By A. A. Eaton. 



SEVENTEENTH PAPER. 

 Varieties of Equisetum Variegatum. 

 2. Ahskanum A. A. Eaton. Aspect of small hiemale. 

 Rootstocks dull black ; roots densely brown felted ; stems 

 tufted, 6 to 32 inches tall, 1 to 2 lines wide, usually erect, 

 decumbent or assurgent in small forms, 8 to 12 angled, 

 deeply and broadly grooved, occasionally branched the second 

 year ; branches often 6 inches long, short if fruited ; inter- 

 nodes 1 to 2 inches long, dark green, often purple tinged. 

 Ridges with a deep carinal groove and each angle with a row of 



-flint dots. Stomata in one rowed series, each stoma connected 

 with its opposite at top and bottom by a row of rosulae, covered 

 and nearly obsolete in old stems ; sheaths short, tight, green at 

 first except black at base of teeth, developing a broad black band 

 above ; basal sheaths often all black ; old sheaths becoming cine- 

 reous at top. Leaves 4 to 6 angled; teeth broad, rigid, 

 not articulated, erect, persistent, black with a broad or narrow, 

 often deciduous border, 4 to 6 angled, the carinal groove very 

 deep, tipped with a rough, black, deciduous awn. Upper sheath 

 broadly campanulate, black, with about 10 very broad. 4 to 8 

 ribbed leaves : spikes nearly sessile, half an inch long, usually 

 black, with a very large apiculate point, the sporophyls often 

 deciduous, leaving the axis naked after sporosity. Spores ripe 

 in July and August; centrum 1-3 to 1-2 the diameter of the stem, 

 vallecular bast stout, 3 to 5 cells broao!, meniscus-shaped, reach- 

 ing the central cavity, the carinal pointed, of about equal height. 



4he green parenchyma continuous under it. Anatomy similar to 

 typical variegatum. 



From Washington, by springs, Columbia River. Suksdorf, 

 2099. to British Columbia at New Westminster, on wet sand and 

 silt, A. J. Hill, and Sicamous, on rotten mossy logs and in bogs 

 with Philonotis fontana, M. J. Finlayson, east to Selkirk 

 Mountains at Glacier, Canada, W. M. Canby, northward to 

 Alaska, where it was abundantly collected by members of the 

 Harriman expedition in 1899 at Muir Inlet, Glacier Inlet, Disen- 

 chantment Bay, Hidden Glacier Inlet and Russell Fiord. Khantaak 



