No, H^H^^Il?. BRYOFHYTES CV CONNECTICUT. 79 



22. Chlorophyll cells trapezoidal in cross section; the walls 

 not thickened, and the broad base toward the outer 

 surface of tbe leaf; hyaline cells strongly convex toward 



the inner surface S. dasyphyllum 



Chlorophyll cells barrel-shaped to rectangular in cross 

 section, equally free toward both surfaces, and with the 



free walls usually thickened 23 



2^. Cortex of stem consisting of 2-several layers of cells.... 24 

 Cortex of stem consisting of one layer of cells 25 



24. Stem leaves small, not more than i mm. long, fibrils 



present only near the apex; branch leaves secund.... 



S. contortum 

 Stem leaves larger, 1.5-2 mm. long, fibrils usually abundant 

 throughout; branch leaves not secund S. platyphyllum 



25. Branch leaves with many pores, at least on the outer 



surface; pores frequently in bead-like rows 26 



Branch leaves with very few or no pores S. obesum 



26. Pores few or lacking on the inner surface 27 



Pores numerous on both surfaces, especially on the outer; 



stem leaves' 1-2 mm. long S, rufescens 



2y. Stem leaves less than i mm. long, hyaline cells rarely 



septate S. subsecundum, 



Stem leaves 1-1.5 mm. long, hyaline cells often septate 



S. inundatum 



28. Chlorophyll cells of branch leaves usually free toward 



both surfaces of the leaf 29 



Chlorophyll cells of branch leaves enclosed by the hyaline 

 cells, equidistant from both surfaces of the leaf, and 

 elliptical in cross section; hyaline cells smooth or 

 faintly papillose on the lateral walls S. medium 



29. Chlorophyll cells triangular or trapezoidal in cross section, 



the base toward the inner surface of the leaf and not 

 thickened; hyaline cells strongly convex toward the 



outer surface 30 



Chlorophyll cells more or less elliptical in cross section, 

 cell cavity almost central, and both surface walls 

 strongly thickened; hyaline cells more strongly convex 

 toward the outer surface of the leaf than toward the 



inner surface, and papillose on the lateral walls 



S. papillosum 



30. Chlorophyll cells broadly triangular to trapezoidal; hyaline 



cells with irregular bands of thickening on the lateral 



walls S. imbricatum 



Chlorophyll cells narrowly triangular; hyaline cells smooth 

 on the lateral walls S. cymbifolium 



