BARNES NORTH AMERICAN MOSSES. 181 



II. Cells of the exothecium prosenchymatous ; seta often yellow; 

 costa usually broad and indistinct below. 



A. Seta red. 



Leaves from a sheathing base, squarrose D. crispa, 64. 

 Leaves not sheathing nor squarrose. 



Mostly erect, capsule cernuous .... D. snbulata, 66. 



Secund, capsule erect D. eurvata, 67. 



B. Seta yellowish. 



Capsule symmetric, erect ..... D. Fitzgerald!, 60. 

 Capsule cernuous. 



Strumose . D. cerviculata, 65. 



Notstrumose . . . ." . . '. D. heteromalla, 66. 



DICRANUM, p. 67.1 



In this genus the structure of the costa is of diagnostic value. It is 

 either composed of similar cells (homogeneous), or composed of large 

 parenchyma cells and small sclerenchyma cells (stereids). The large pa- 

 renchyma cells (guides = "Deuter" of Lorentz 8 ) form a row (seldom double) 

 in the middle of the costa touching each other tangentially. They are 

 comparatively large, but little thickened and either empty or starch-bear- 

 ing. 3 



I. Monoicous, stems radiculose only at base, costa long excurrent, 



homogeneous. 



Capsule erect, not strumose. 



Striate and furrowed when dry . . . D. hyperboreum, 4 64. 

 Neither striate nor furrowed when dry . . D. fulvellum, 68. 

 Capsule cernuous, strumose. 



Leaf cells not papillose, capsule oblong-cylindric D. Starkii, 68. 



Leaf cells with papillae over partitions, capsule short-ovate. 

 Leaves falcate-secund . . ; . . D. falcatum, 5 68. 

 Leaves spreading . . . . . . . D. Blytii, 68. 



1 Arranged by DE. RODNEY H. TEUE. 



2 Pringsheim's Jahrb. f. wissensch. Bot. 6: 374. 

 3 Limpricht: Die Laubmoose 23. 



4 See Appendix, no. 65. 

 6 See Appendix, no. 65a. 



