— 88 — 



cells are mostly oval to rhomboidal seldom more than twice lon.^er than broad 

 and in margin below slightly transversely elongated. The vein is broad 

 below and extends )^ up the leaf or sometimes shorter and forked above. 

 Sterile (7021. 



Hypnum aviblyphylliirn, R. S Williams sp. nov. 



Dioicous. Growing in water up to 3.5 dm. high, with mostly short, sub- 

 pinnate branches hooked at apex. Cross sections of stem 5-sided with dis- 

 tinct angles, a poorly developed central strand of 3 or 4 small cells and outer 

 walls of I 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 incurved. 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. Median leaf-cells .005 or .006 mm. wide and mostly .035 to 

 .060 mm. long. Younger branch leaves narrowerly 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 I or more. Seta up to 6 cm. long. Capsule 2.5 by i mm., with short up- 

 right 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 mem- 

 brane at endostome scarcely ^ the teeth m 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 round- 

 ish to short oblong, up to .040 mm. long. Minutely roughened spores up to 

 .016 mm. (Plate 24.) 



This species is intermediate between exaiuiulatuin and pseudostramin- 

 eum. From the first it differs in the short, broadly-pointed leaves, the angu- 

 lar 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. 



Dawson, in swamp water, in fine fruit July 17, 1898 (746). 



Hypnum subplicatile (Lindb.) Limpr. Lake Lindeman, on damp rock 

 and earth. This plant is very close to callichrouin but differs in being rather 

 smaller with regularly pinnate branches, leaves wider just above the base 

 and abruptly narrowed to the insertion and capsule shorter. Cross sections 

 of stem show an indistinct central strand and walls of a row of thin outer 

 cells next about 3 rows of thick-walled cells. Median leaf -cells slightly ver- 

 micular, about .005 mm. wide and .040-060 mm. long, alar cells mostly form- 

 ing a small but distinct, convex, pale cluster. Stem leaves entire, borders 

 flat, terminal branch leaves minutely serrulate, perichaetial leaves gradu- 

 ally narrowed to long, serrulate, slender point. 



According to Limpricht this species has been previously collected on the 

 island of Sachalin and in eastern Russia (751). 



