210 American Midland Naturalist Monograph No. 6 



when moist erect-spreading or open-erect but never secund; stem-leaves plicate, 

 from a narrowed and decurrent base, mostly with revolute margin, entire or 

 apically toothed; costa strong, mostly incomplete, rarely excurrent, sometimes 

 dorsally rough, leaf-cells rather uniform, rounded to oval- or oblong-hexagonal, 

 both sides numerously papillose or uni-papillose dorsally or on both sides; 

 branch-leaves of first order often similar to stem-leaves, those of the second or 

 third order smaller, mostly lance-ovate, with the costa weaker and shorter; 

 inner perichaetial leaves pale, appressed, mostly lanceolate and plicate, often 

 with a prolonged and filiform apex, sometimes with ciliate margins, costa in- 

 complete, cells elongate, smooth: seta elongate, castaneous or red, smooth or 

 rough; capsule inclined to horizontal, oval-oblong to cylindric, more or less 

 arcuate, brown to yellow, drying constricted below the mouth; annulus some- 

 times persistent; peristome-teeth basally confluent, lance-subulate, bordered, 

 cross-striate, numerously trabeculate; inner peristome yellow to orange, smooth 

 or finely papillose, with prominent carinate basal membrane, segments as long 

 as teeth, carinately split at least in part; cilia 2-4, nodose to appendiculate, or 

 sometimes rudimentary, or none; lid convex-conic, obliquely rostrate; calyptra 

 cucullate, mostly smooth; spores .007-.010 mm or .012-. 016 mm. 



A widely distributed genus of about 160 species, on tree-trunks, rocks, or 

 earth; about 25 species reported for North America; at least 4, probably more, 

 in our region. 



Key to the Species 



A. Delicate, small, not over 5 cm; 1-2 pinnate B 



A. Larger, up to 10 cm; 1-3 pinnate C 



B. Branchlets papillate; leaf-cells about .006 mm: seta 1-1.5 cm long ....2. T. pygmaeum 



B. Branchlets smooth; cells about .009 mm: seta 2-3 cm long 1. T. minutulum 



C. Stems simply pinnate; plants ascending in tufts 3. T. abietinum 



C. Stems 2-3 pinnate, forming flat mats d 



D. Leaf-margin revolute; costa not filling entire apex of leaf E 



D. Leaf-margin plane; costa of stem-leaves filling the entire ap>ex; perichaetial leaves 



not ciliate 4. T. recognitum 



E. Stem-leaves lance-acuminate, from a triangular-ovate base; perichaetial leaves ciliate 



7. T. delicatulum 



E. Stem-leaves long-lance subulate; perichaetial leaves not ciliate 



6. T. Philiberti 



E. Stem-leaves shortly and broadly acuminate; perichaetial leaves not ciliate 5. T.Alleni 



1. Thuidium minutulum [Hedwig] Bryologia Europaea 

 (Hypnum minutulum Hedwig) 

 Plate XXXIX 



Small, slender, simply pinnate; stems irregularly divided, not over 3 or 4 

 cm long, both stems and branches smooth, bearing rather few linear-oblong 

 simple paraphyllia only about 2 to 5 cells high, notched at apex; stem-leaves 

 distant, deltoid, acuminate or apiculate, somewhat revolute on the borders, 

 rather opaque, about 0.6 0.8 mm long; costa strong, ending near the apex; 

 median leaf-cells irregularly polygonal to quadrate-hexagonal, the marginal 

 somewhat larger and sometimes transversely elongate, all leaf-cells incrassate, 

 pluri-papillose, the apical cell with 2 to 5 marginal papillae; branch-leaves 



