—4i— 



lae, the whole often overlaid with a coat of silex which makes 

 it very smooth; lumen of epidermal cells wide, the edges little 

 rayed; nodes contracted when dry; sheaths long, widened up- 

 ward, the leaves keeled on the back for y 2 to 2-3 the height, then 

 often flat, the edges often rising into ridges in those of the 

 lower sheaths; teeth dark brown, the basal shining, usually 

 cohering by the tops and torn off by the growth of the stem; 

 when present they usually cohere by their tips into groups and 

 fade to papery whiteness. They leave black, shining, rigid, cen- 

 trally grooved, triangular, membranous bordered bases in falling 

 which incurve at the tips and form a narrow black and white 

 limb to the sheath. 



Central cavity wide, occupying ^ the diameter of the stem, 

 the carinal usually small or often obsolete, the vallecular also 

 small or medium. The vallecular bast cuts the green paren- 

 chym to the cavity, equaling or exceeding the carinal, which 

 occupies a small triangle under the epidermis of the keel, the 

 green parenchym thus being of a Y-shape between and above 

 the vallecular holes. A section of the sheaths shows a linear 

 streak of green parenchyma each side of the bast which cor- 

 responds to the carinal hole of the stems. Spikes included in the 

 upper sheaths or slightly exserted, rounded, or slightly apicu- 

 late. 



This species can readily be separated from robustum, with 

 which it grows, by its longer, spreading sheaths, its annual 

 stems, and especially its anatomy, the vallecular bast being 

 larger than the carinal. while in robustum this is reversed, the 

 carinal bast extending nearly to the carinal hole, the vallecular 

 bast being small and the green parenchyma continuous between 

 it and the hole. The section of this is very like that of variega- 

 tum and ramosissimum, but the former has a very small central 

 hole and the latter is intermediate. Indeed, there appears to 

 be a regular gradation from variegatum, through the round- 

 angled variety Nelsoni to this species and ramosissimum, and at 

 times it is difficult to draw the line. Milde had an imperfect idea 

 of this species and figured (Mon. I., XXXII., fig. 3) a species 

 with two-angled ridge and stout carinal bast. I am not certain 

 as to the identity of his plant, but it is assuredly not laevigatum. 



