174 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



Stem leaves not enlarged from the base upwards, apex 

 frequently cucullate and fringed. 



Hyaline cells not divided S. obesuin, 16. 



Hyaline cells with 1-2 cross walls . . . S. dasyphyllum, 17. 



2. Branch leaves with few pores on the inside, outside with numer- 

 ous pores in head-like roivs. (3) 



a. Chlorophyllose cells of branch leaves isosceles-triangular, or 



trapezoidal in cross section; mostly exposed on the inner 

 face S. microcarpum, 18. 



b. Chlorophyllose cells of branch leaves quadrate or barrel-shaped, 



central and exposed on both faces, (c) 



Stem mostly simple, rarely a single divergent branch S. cyclophyllum, 22. 

 Stem fasciculate-branched. 

 Cortex of one or (in part) two cell layers . S. subsecundum, 19. 



Cortex of two to several cell layers. 

 Hyaline cells with abundant fibrils, stem leaves large 



(1.3-1.4 mm. long) .... S. platyphyllnm, 19. 



Hyaline cells without fibrils, or with fibrils only at apex, 



stem leaves smaller (.86 mm. long) . . S. contortum,i 19. 



Chlorophyllose cells triangular or trapezoidal, exposed on the 



outer face. 



Branch leaves ovate-lanceolate, plicate . . . S. plicatum, 20. 

 Branch leaves round ovate, not plicate . . . S. Orlandense, SI. 



3. Branch leaves with abundant pores on both faces. 



Chlorophyllose cells triangular or trapezoidal in cross section, 

 mostly exposed on outer face (sometimes on both). 

 Hyaline cells much divided, chlorophyllose cells 



triangular S. Mobilense, 2£. 



Hyaline cells once divided, chlorophyllose cells 



trapezoidal, free on both faces . . . . S. simile, 23. 

 Chlorophyllose cells quadrate or barrel-shaped, central 



or exposed on both faces S- rufescens, 24. 



1 8, laricinum Spruce, L. & J. Man. 19. 



