—23— 



herbarium. I take pleasure in naming this species for Mr. 

 James H. Ferriss, whose energy in collecting and cultivating 

 ferns has greatly increased our knowledge of these plants, and in 

 whose collection I first saw this species growing. 



THE GENUS EQUISETUM IN NORTH AMERICA. 



By Alvah A. Eaton. 



SIXTEENTH PAPER. 

 E. Yariegatum Shleicher. 



Stems naked or rarely branched, rough or smoothish. angles 

 4 to 12 bearing two lines of tubercles or rarely cross bands ; 

 sheaths campanulate (in type) or cylindrical, short or elongated, 

 never truncate ; leaves distinctly four angled, with a deep carinal 

 groove which is decurrent into the stem ridges, basal half of 

 teeth persistent, oblong or ovate, membranaceous with dark 

 median-grooved center, ending in a deciduous subulate rough 

 point or (in Jesupi) with persistent points, connivent in groups; 

 ridges broad, biangulate, with two rows of tubercles, rarely 

 with bands ; grooves twice as broad with stomata in one rowed 

 series and bands of rosulae. 



In its typical state this is a very distinct species, but it grades 

 insensibly into hicmalc on the one hand and lacvigatum and 

 ramosissimum on the other. Taken by itself variety Jesupi would 

 fall in hicmalc after variety Docllii, which it strongly resembles ; 

 but it is even more like the European variegatum IVilsoni, and 

 the European trachyodon connects the latter to forms like .llas- 

 k anuin, which in turn lead to the type. Milde notes some Europ- 

 ean forms that run into ramosissimum, and our variety Nelsoni 

 could as well be placed under laevigata m, but the small centrum 

 and rosulae. make it more natural to place it here. 



The bast of typical variegatum is similar to that of lacviga- 

 tum, the vallecular being longer, often meniscus-shaped, cutting 

 the parenchyma to the cavity. In the section to which Jesupi be- 

 longs the carinal is predominately larger, but this character is 

 seldom constant in this species even in the same cross-section. 

 Milde considers the decurrent median groove of the sheaths as 

 diagnostic. The species may be tabulated as follows : 



