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cordate, narrowly acuminate; median leaf cells roundish hexagonal with 2 

 to 5 small bead-like papillae on each surface ; monoicous ; capsule cylin- 

 drical, straight, or but slightly curved; operculum conic- rostrate ; spores 

 maturing in autumn and winter. Var. acpstivalc (Aust.) ; stems not so closely 

 pinnate ; capsule oblong-cylindrical, inclined to horizontal ; operculum shorter 

 beaked — From Canada to North Carolina and from Vermont to Wisconsin. 



Thuidium ABiEi inum (L.) Br. & Sch. Plants rather large, stiff, in dense 

 tufts, usually on rocks and stones, rarely on the ground ; stem leaves broadly 

 ovate, acuminate, deeply biplicate, margins serrulate; median leaf cells 

 oval-rhombic; dioicous; capsule narrowly cylindrical, curved; operculum 

 longcoric. From Greeland to Virginia and from New Foundland to British 

 Columbia. Fruiting in Colorado and Montana and fruiting freely in Alaska. 



Thuidium recogniti'm (Hedw.) Lindb. Much difficulty has been ex- 

 perienced in discriminating between this and the following species. They 

 not infrequently grow together. Intermediate forms, however, are rare, 

 probably owing to the difference in their fruiting seasons. The broadly 

 triangular, auriculo-cordate. abruptly acuminate stem leaves are sulcate 

 when dry, spreading-recurved when moist, usually plane on the serrulate 

 margins; costa subpercurrent, somewhat spreading at apex; median leaf 

 cells oblong-rhombic, passing to oblong-linear in the acumen; dioicous: 

 capsule cylindrical, curved : operculum rostellate. On the ground, rotten 

 wood, stones and rocks. Spores mature in July. From Labrador to British 

 Columbia southward, rare or absent on the Pacific slope and in the Gulf 

 States. 



THumiuM DEi.icATi'LUM (fy. ) Mitt. Stem Icavcs triangular-ovatc, rather 

 gradually acuminate, appressed when dry, erect-spreading when moist, 

 margins serrate, more or less recurved : costa vanishing in the acumen : 

 median leaf cells quadrate-oblong to oval rhombic : perichaetial bracts 

 cilate: dioicous; capsule cylindrical, curved; operculum conic-rostrate; 

 spores maturing in winter. On the ground, rotten wood, stones and rocks. 

 From Labrador to British Columbia southward through the United States, 

 rare west of the Rocky mountains. 



Thuidium Philiherti Limpr. The distinguishing character of this rare 

 species is the hyaline, filiform acumination of the stem leaves which are 

 somewhat intermediate between those of T. recognituni and T. delicatu- 

 lum : the median leaf cells are quadrate-oblong rather than oblong-rhombic : 

 costa thin, disappearing above the middle; dioicous; capsule cylindrical, 

 curved: annulus not clearly differentiated ; operculum conic-rostrate ; spores 

 maturing in October. On swampy ground and about the base of small 

 trees in wet places. New Jersey, Pennsylvania, Ontario and New Brunswick. 



Thuidium Virginianum (Brid.) Lindb. {T. gracile var. Lajicasfriense 

 vS. & L.) Plants small, dark or dirty green, in open woods, on the ground 

 or about stumps and roots of trees. Margins of the roundish ovate stem 

 leaves erose-dentate below, serrate above ; acumen of the branch leaves 

 short, broad, sharply serrate : median leaf cells quadrate-hexagonal; mon- 



