1.Plants with stems and leaves… 2
2.A) Leaves equally spaced around stem, or in two ranks with a midrib… Musci (p. 23)
1. B) Gametophytes present with obvious leaves… 2
2. B) Leaf cells of one kind (green), or if of two kinds, branches never in clusters...3
3. B) Leaves attached all around the stem (foliate stems sometimes flattened [complanate])…7
7. B) Leaves without lamellae or filaments on the adaxial surface of the costa (but propagula sometimes present)…23
23. B) Leaves never lobed, flattened (although sometimes concave with margins inrolled or recurved)…24
24. Leaves with a single costa to at least midleaf…114
114. B) Plants prostrate to erect, simple to pinnately branched…121
121. B) Plants greenish to blackish, on various substrates; capsules cleistocarpous or operculate, never valvate...123
123. B) Leaves erect to squarrose; plants occurring in various habitats…124
142. B) Plants greenish to blackish, rarely whitish; leaves usually with conspicuous lamina, if not green cells and hyaline cells of about equal size with only a single layer of hyaline cells on either side of the green cells…144
144. B) Leaf margins plane to recurved…149
149. B) Plants mostly larger, occurring on various substrates, mostly not ephemeral, or if so, capsules exserted… 161
161. B) Neck of capsules considerably narrower than urn; occurring on various substrates…164
164. B) Leaves all of one kind…166
166. B) Capsules operculate; plants rare to common…169
169. B) Cells without nodulose-wavy walls, or if present only near insertion…170
170. B) Leaves without hair-points, or if with hairpoints not hyaline…181
181. B) Costa narrower, or if broad then ending below the leaf apex and not filling it (or if broad then pleurocarpous)…187
187. B) Plants acrocarpous (sporophytes terminal); stems erect, not branched or occasionally branched beneath inflorescences…280
280. Capsules large, sessile, asymmetric…281
281. B) Costa smooth or toothed at back, not ridged…283
283. B) Rhizoids inconspicuous or if obvious, never obscuring the stem…287
287. B) Plants greenish, occurring in various habitats, rarely on wet rocks by streams, with or without propagula…290
290. B) Hyaline basal cells if present extending more or less equally up the margins as costa or farther up the costa…293
293. B) Plants not glaucous or bluish…294
294. Leaves bordered by 2 or more rows of elongate cells…295
295. B) Leaf margins toothed…300
300. B) Leaves without expanded base, without hyaline cells…301
301. B) Leaf margins with paired teeth…302
302. B) Leaf cells flat…303
