1	"Costa single and extending considerably above mid-leaf"	2
1	"Costae double, ending at or below mid-leaf, sometimes almost absent"	7
2	"Paraphyllia present, abundant on larger stems"	3
2	"Paraphyllia absent"	4
3	"Leaves plicate or wrinkled; paraphyllia attached to leaf bases and to stems, lobed with the lobes narrowly lanceolate to linear; plant of bogs or fens"	"Helodium blandowii"
3	"Leaves not plicate; paraphyllia not attached to leaf bases but rather on stem, lobed into uniseriate filaments with the ultimate cell coronate-papillose; plants of mesic sites"	"Thuidium recognitum"
4	"Leaves strongly heterophyllous with stem leaves relatively broader and more decurrent, markedly larger than branch leaves; stem leaves strongly spreading to almost squarrose"	5
4	"Leaves not so heterophyllous; stem leaves, if spreading, similar in orientation to branch leaves"	6
5	"Plant regularly plumose with a single main stem from which arises shorter, nearly unbranched, lateral stems; plant mainly of coastal moderately low elevation sites"	"Kindbergia oregana"
5	"Plant irregularly branched or tri- to tetra-pinnate; plant mainly of higher elevation, or of deeply shaded sites"	"Kindbergia praelonga"
6	"Leaves strongly rugose"	"Rhytidium rugosum"
6	"Leaves closely many times plicate"	"Trachybryum megaptilum"
7	"Branched paraphyllia present and densely arranged on stems and branches"	8
7	"Paraphyllia absent"	9
8	"Plant regularly many times pinnately branched with the branches arranged in a single plane; leaves of ultimate branches broadly ovate, mostly less than 1 mm long"	"Hylocomium splendens"
8	"Plant sparingly and irregularly branched with the leaves of the branches not significantly smaller than those of the stems, mostly about 4 mm long"	"Rhytidiopsis robusta"
9	"Leaves bluntly rounded at apex, never plicate or squarrose"	"Pleurozium schreberi"
9	"Leaves acute to acuminate at apex, often plicate or squarrose"	10
10	"Leaves falcate-secund, ascending or weakly spreading, plicate, not at all papillose or prorate; tips of main stems arched downward toward the substratum"	"Rhytidiadelphus loreus"
10	"Leaves not falcate, squarrose or broadly spreading, if plicate, the cells sharply prorate above mid-leaf; tips of main stems of well developed plants mostly ascending"	11
11	"Leaves strongly plicate; cells sharply prorate at least above mid-leaf"	"Rhytidiadelphus triquetrus"
11	"Leaves not plicate; cells smooth"	12
12	"Plant of lawns and other anthropogenic sites, pinnate but with the branches rather distantly spaced"	"Rhytidiadelphus squarrosus"
12	"Plant of natural bogs, carrs, and other wet places; branching inserted regularly in the axils of every third or fourth leaf on each side of stem"	"Rhytidiadelphus subpinnatus"