78 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
21. 
CONNECTICUT GEOL. AND NAT. HIST. SURVEY. ([Bull. 
Chlorophyll cells narrowly trapezoidal or rectangular in 
cross section, free at both surfaces, but with the surface 
walls strongly thickened (Squarrosa, p. 81)..........-- 14 
Chlorophyll cells with the free walls scarcely, if at all, 
thickened; branch leaves erect-spreading* (CUSPIDATA, D. 
G2): chard wee uur) ce ula iroeterames oor etarg. apart ata thas owas es 15 
Plants large, monoicous; branch leaves mostly squarrose 
from) the middle: ici. sscwmeaceanan cee sien S. squarrosum 
Plants medium-sized, dioicous; branch leaves more or less 
imbricatet, not squarrose .............- eben eens S. teres 
Chlorophyll cells triangular in cross section, often enclosed 
toward the inner leaf surface by the hyaline cells...... 17 
Chlorophyll cells trapezoidal in cross section and free on 
Doth: SUPiaCESe cccccive cane meena geaud davnnecn sabes cages 16 
Pores numerous on outer surface of the branch leaves, 
frequently large and usually in rows............ S. Dusenii 
Pores mostly lacking on outer surface of the branch 
leaves, when present, small and restricted to the angles 
Of tHE COIS: wijeincwieca.camiaw ciwslos tse setae S. cuspidatum 
Cortex well differentiated from the central strand........ 18 
Cortex not well differentiated from the central strand.... 19 
Stem leaves lacerate-fringed at the apex...... S. Pulchricoma 
Stem leaves toothed at the apex..... paged eck S. Torreyanum 
Pores on outer surface of the branch leaves in the apical 
half restricted to the angles of the cells...... S. recurvum 
Pores on outer surface of the branch leaves in the .apical 
half occurring in the angles and also along the lateral 
margins of the cells...................0000- S. parvifolium 
Chlorophyll cells enclosed toward one or both surfaces of 
the leaf by the hyaline cells, elliptical or spindle-shaped 
in cross section; branch leaves squarrose from the 
middle (RIGIDA, p. 81)......... eee cece cece eee cette eees 2 
Chlorophyll cells free toward both surfaces of the leaf; 
branch leaves more or less secund or falcate (Sus- 
SECUNDA; ‘D., 85). x ostncvemanieeere x seeesecmbesweees econ 22 
Chlorophyll cells elliptical in cross section and enclosed 
toward both leaf surfaces by the hyaline cells...... 
. S. compactum 
Chlorophyll cells spindle-shaped in cross section and 
enclosed toward the inner surface of the leaf by the 
hyaline cells; the outer wall free, but very strongly 
thickened) os asus camerscasaws siwev esas ames eas S. Garberi 
*s. dasyphyllum may be looked for here, 
