(!39) 



Sections of stem show at the surface a layer of thin-walled 

 cells next to several rows of thickened cells and mostly a 

 central strand of 4 or 5 small cells, sometimes not distinct, 

 however. The costa is in section plano-convex. Plates of 

 teeth finely cross-lined (745). 



Hypnum amblyphyllum R. S. Williams sp. nov. 



Dioicous. Growing in water up to 3.5 dm. high, with 

 mostly short, subpinnate branches hooked at apex. Cross 

 sections of stem 5-sided with distinct angles, a poorly devel- 

 oped central strand of 3 or 4 small cells and outer walls of 1 

 or 2 rows of thickened cells. Leaves below more or less 

 spreading, flexuous and twisted, toward the tops of the stems 

 and branches falcate-secund with the tips often abruptly in- 

 curved. Stem leaves about 2.25 mm. long, serrulate all 

 round, distinctly long-decurrent, ovate-lanceolate with broad, 

 obtuse point, not plicate, somewhat concave, especially 

 toward apex. Costa extending § up, slightly convex on 

 back. Alar cells often inflated nearly to costa and some 

 small, nearly quadratic cells at margin just above the alar 

 cells. Medium leaf-cells .005 or .006 mm. wide and mostly 

 .035 to .060 mm. long. Younger branch leaves narrowly 

 lanceolate with very short costa. Perichaetial leaves not 

 plicate, closely sheathing, but little larger or more pointed 

 than stem leaves, entire, with faint costa extending up § or 

 more. Seta up to 6 cm. long. Capsule 2.5 by 1 mm., with 

 short upright collum, but much curved and nodding above. 

 Lid acutely conical, its height less than basal diameter. No 

 annulus. Peristome teeth broadly hyaline bordered above, 

 outer plates finely punctate below. Basal membrane of en- 

 dostome scarcely ithe teeth in height with solid segments and 

 2 or 3 nodose cilia between. Transversely elongated cells 

 about mouth of capsule in 3 or 4 rows, the cells below 

 roundish to oblong. Stomata roundish to short oblong, up 

 to .040 mm. long. Minutely roughened spores up to .016 

 mm. (Plate 24.) 



This species is intermediate between cxaunulalinii and 

 peicdostra?nineum. From the first it differs in the short, 

 broadly-pointed leaves, the angular stem with fewer thickened 

 cells in the outer walls and leaf-cells not pitted. The 

 second differs in being monoicous, with entire, not decurrent 

 leaves and not angular stems. 



