CHARACTER STATES OF THE DATA SET

The character states scored for the data set are listed below; (R) = reduction-related character, of which there are 22 and weighted lower than other characters in most cladograms, (0´) = character not used at all in Cladogram 15 (i.e., not phylogenetically informative), (1´) = character occurred once in Cladogram 15 (i.e. phylogenetically very informative), and * = the hypothesized plesiotypic character state for the Pottiaceae. Character numbers correspond to the those in the data matrix used with Hennig86, and begin with zero.

0. (R, 0´) plant conflux

0. gregarious or scattered

1. *caespitose, usually in a mat or turf

1. (R) length of stem

0. short, less than 1.0 cm, usually less than 0.6 cm

1. *relatively long, usually 1.0 cm or greater

2. (1´) stem transverse section shape

0. *rounded-pentagonal

1. triangular

3. stem central strand presence

0. absent

1. *present

4. stem sclerodermis presence

0. *not or little differentiated from central cylinder cells

1. clearly differentiated

5. stem hyalodermis

0. *absent

1. present (sometimes small)

6. (1´) axillary hair basal cell walls

0. hyaline and all cells of hair similar

1. *of 1 or more cells with thicker or darker colored walls

7. leaves when dry

0. tubulose

1. *occasionally channeled but not distinctly tubulose

8. leaves when wet

0. appressed to weakly spreading

1. *widely spreading to squarrose

9. (0´) leaves, size gradation

0. *gradually becoming larger distally on stem

1. rosulate (abruptly larger distally)

10. leaf shape

0. long-triangular to linear-lanceolate

1. *lanceolate

2. broadly ligulate-elliptical to spathulate

11. (R) leaf length

0. less than 1.5 µm

1. 1.5 µm to 3.0 µm

2. *3.0 µm or more

12. leaf ventral surface above midleaf

0. *nearly plane to broadly channeled

1. keeled

13. rather deep, narrow groove along costa

0. *absent

1. present

14. margins

0. sharply incurved

1. *incurved or involute

2. plane

3. recurved to revolute

15. marginal toothing

0. entire or minutely and evenly crenulate

1. denticulate or serrulate

2. *strongly toothed

16. margins specially denticulate

0. *not denticulate only below

1. denticulate only near leaf base or at top of leaf sheath

17. (1´) upper marginal cells differentiation

0. *same number of layers as medial cells

1. always differentiated as a bistratose (or more) border

18. upper marginal cells, elongation

0. *not longer than medial cells (sometimes larger)

1. rectangular and clearly longer than medial cells

19. (1´) leaf apex

0. rounded

1. *acute to acuminate

20. leaf apex ventral surface

0. *flattened, channeled or keeled

1. cucullate

21. (R) leaf base

0. little differentiated in shape

1. ovate to elliptical

2. *sheathing the stem and commonly oblong and with “shoulders”

22. (1´) costa

0. ending before the leaf apex

1. *percurrent or apiculate or short-excurrent as a mucro

2. excurrent as an awn

23. costal ventral cells viewed from above

0. *quadrate to very short-rectangular, occasionally in many layers

1. longitudinally elongate 3:1 or more

24. number of rows of cells across ventral surface of costa

0. usually 2 but up to 4

1. 4–6

2. 6–10

3. *usually 10 or more

25. shape of transverse section of costa

0. *round to semicircular

1. distinctly flattened, usually reniform

26. ventral stereid band

0. absent

1. *present

27. (1´) size of ventral stereid band

0. *smaller than the dorsal or of nearly equal size

1. larger than the dorsal

28. transverse section of dorsal stereid band

0. round or semicircular

1. *clearly flattened or ventrally indented, reniform or crescent-shaped

29. ventral costal epidermis

0. absent

1. *present

30. dorsal costal epidermis

0. absent

1. *present

31. guide cells

0. usually 0

1. 2–6

2. *commonly more than 6

32. (0´) number of guide cell layers

0. *1–2

1. 3 or more

33. hydroid strand

0. absent

1. *present

34. (R, 0´) ventral costal outgrowths

0. *absent or not a bulging pad of cells

1. a bulging pad of cells

35. (R, 1´) ventral costal filamentous outgrowths (note: exclusive of lamellae)

0. *absent or not of filaments

1. of separate filaments three or more cells in length

36. width of medial upper laminal cells

0. *small to medium sized, 7–14 µm

1. rather large, 15–17 µm

2. very large, 18–25 µm

3. extremely large, 25 µm or more

37. (0´) length to width ratio of medial upper laminal cells

0. *1–2:1

1. 3–4:1 or more

38. (0´) upper laminal cell walls

0. *thin to evenly thickened, lumens quadrate to rounded

1. trigonous or porose, lumens irregularly angular or stellate

39. superficial walls of upper laminal cells

0. flat or very weakly convex on both sides

1. strongly convex to bulging on both sides

2. *ventrally bulging-mamillose, weakly convex dorsally

40. layering of upper laminal cells

0. *medially unistratose

1. medially bistratose, at least in patches

41. (R, 0´) dorsal superficial laminal cell walls

0. *about same thickness as the ventral or weakly thicker near costa

1. throughout distinctly thicker than the ventral

42. (1´) upper laminal papillae

0. absent

1. *present

43. kind of papillae when present

0. simple, hemispherical

1. *bifid to multifid to columniform to capitulate

44. number of papillae per lumen when present

0. one or occasionally two

1. *2–6, usually bifid or multifid

2. many, usually 6 or more, simple or bifid

45. basal cell group

0. not or little differentiated from upper medial cells

1. *clearly differentiated approximately straight across leaf or rising higher medially

2. differentiated as a vee, with at least laterally differentiated cells rising higher marginally as a border tapering distally

46. propagula presence

0. *always absent or extremely rare and associated with unusually moist conditions

1. often present and characteristic

47. (1´) position of propagula when present

0. not borne on rhizoids as brood bodies, or absent

1. borne on rhizoids as brood bodies

48. position of propagula when present

0. not born in leaf axils, or absent

1. borne in axils

49. (1´) position of propagula when present

0. not borne on leaf costa or lamina, or absent

1. born on leaf costa or lamina

50. shape of axillary propagula when present

0. not clavate or filamentous

1. clavate or filamentous

51. shape of axillary propagula when present

0. not branching or stellate

1. branching or stellate

52. (R) sexual condition

0. *dioicous

1. monoicous

53. (0´) perichaetium

0. *terminal on main axis

1. lateral on main axis at ends of very short branches

54. perichaetial leaves

0. *similar to cauline leaves or occasionally smaller or somewhat enlarged

1. distinctly different in size or morphology, sometimes strongly sheathing

55. (R) length of seta

0. nearly absent to short, less than 1 cm

1. *elongate, 1 cm or longer

56. (R) seta twist

0. *usually twisted clockwise

1. never twisted

2. usually twisted counterclockwise

57. (R) theca length

0. short, 1.5 µm in length or less

1. *usually between 1.5 and 3.5 µm in length

2. 3.5 µm in length or more

58. (R, 1´) shape of theca

0. spherical and non-apiculate

1. spherical and apiculate

2. *ovoid to cylindrical

59. (R, 1´) capsule dehiscence

0. cleistocarpous

1. *stegocarpous

60. (R, 1´) capsule ornamentation

0. *surface nearly smooth

1. surface evenly mamillose or with distinct protuberances of strongly bulging cells basally or throughout

61. (R, 1´) exothecial cells

0. with walls superficially thickened centrally and lens-like

1. *with evenly thickened superficial walls

62. (R, 0´) capsule

0. cleistocarpous and rupturing mainly along weak transverse walls at butt ends of long-rectangular exothecial cells

1. *rupturing irregularly if cleistocarpous, or stegocarpous

63. (1´) stomates

0. absent

1. *present

64. annulus

0. of weakly differentiated cells

1. *of vesiculose cells, often in two or more rows

65. (R) peristome teeth

0. absent

1. *present

66. (R) peristome teeth when present

0. rudimentary, a low plate or short-elliptical in shape

1. 16, often cleft to near base into two or more rami, or of 16 pairs

2. *32 similar rami

67. (0´) ornamentation of peristome teeth

0. smooth

1. striate or ridged

2. *spiculose or papillose

68. (R) peristome teeth twist

0. untwisted or very weakly so

1. *distinctly twisted

69. (0´) peristome teeth if twisted

0. clockwise

1. *counterclockwise

70. (0´) calyptra ornamentation

0. *smooth or nearly so

1. papillose, distinctly roughened or strongly mamillose

71. (R) length of calyptra

0. short, less than 1 µm

1. 1–3 µm

2. *more than 3 µm

72. (R) spore diameter

0. *8–15 µm

1. more than 15 µm

73. KOH color reaction of upper laminal cell walls

0. essentially yellow

1. essentially orange

2. *essentially red, usually a definite brick red

74. (R, 1´) calyptra shape

0. *cucullate or at least long-conic and cleft, usually more than 1 µm in length

1. mitrate or short-conic and uncleft, commonly lobed, usually less than 1 µm in length

2. campanulate-inflated

Discussion of Character States and Polarity

Outgroups appropriate for analysis need to possess most of the characters of the Pottiaceae, but be sufficiently distant phylogenetically as to share a common ancestor with all genera of the Pottiaceae. Inasmuch as closely related families are much reduced, choosing the appropriate outgroup required considerable analysis, described below. Basically, the rationale was that Timmia and Polytrichum were similar in morphology gametophytically to certain genera of the Pottiaceae but had peristomes of apparently considerable evolutionary distance. The particular haplolepideous genus used here as outgroup that placed these two distant but related genera low in the tree when both pottiaceous and non-Pottiaceae genera were included in the cladogram would be the appropriate outgroup. Ten non-pottiaceous genera were used as outgroups to construct a series of cladograms, which were then evaluated individually and compared. Three genera were similar in gametophyte characters to those of particular apparently non-reduced Pottiaceae, but which have quite different peristomes: Polytrichum (nematodontous), Timmia (diplolepideous) and Ptychomitrium (haplolepideous, like the Pottiaceae). These genera grouped near the base of the tree whenever one or the other of the three were used as outgroup. The characters of these genera are taken as plesiomorphic.

It is more probable that the many character states (75 characters are scored in this study) for each character of large-statured genera of Pottiaceae being in large part identical to that of Polytrichum, Timmia and Ptychomitrium is due to sharing those of a common ancestor than to multiple development of these many identical traits. There is no evidence that such traits are not homologous. On the other hand, the probability that Polytrichum is derived from a diplolepideous ancestor is a position not supported by Edwards' (1979, 1984) extensive evaluations of peristome structure.

In a study of this large number of terminal taxa it is doubtful that many of the characters are globally homologous because of their apparent lack of genetic complexity. These 75 characters were selected for analysis because homology of the character states is supported by similar morphological positions of the states, the fact that the characters remain similar through transformation series intragenerically, and because other characters correlate with them intragenerically. Additional work, however, along the lines reviewed by Wiley (1981, p. 130–158), might reduce homoplasy in the resultant analysis.

The many quantitative characters used in this analysis have assigned states that are not arbitrarily circumscribed, but correspond to perceived discontinuities in ranges of values, meaning that the genera as a whole can usually be easily assigned a particular range of values (e.g. lengths, diameters) for each state of each character. No statistical studies, however, were done beyond an informal evaluation of the actual data for the genera as shown in the data file compiled for the genera during the study, in which discontinuities in measured states for the 76 genera were usually obvious.

The list below evaluates the polarity of each character of the Pottiaceae used in this analysis. There was no one outgroup taxon found that had all states plesiotypic as per this analysis. The plesiotypic state is simply stated as such when candidate outgroups Polytrichum, Timmia and Ptychomitrium have a similar, presumed homologous feature, otherwise exceptions are discussed. Characters for Polytrichum are taken in part from G. Smith (1971); Encalypta in part from Horton (1982 & 1983); Timmia in part from Brassard (1979, 1980 & 1984). Discussions of taxa other than these three are provided to better describe particular shared characters or variations that are probably apotypic and commonly associated with reduction. A hypothetical sister group based on this evaluation was, however, not used as outgroup in the actual analysis.

Polarity of Character States

0. Plants growing caespitose is a plesiomorphic condition; the gregarious or scattered state is associated with reduction.

1. A relatively long (more than 1 cm) stem is plesiomorphic, although Ptychomitrium has a rather short stem.

2. Rounded-pentagonal stem sections are plesiomorphic, being found in Ceratodon, Encalypta, Polytrichum and Timmia; triangular stem sections are rare in the Pottiaceae.

3. Presence of a stem central strand is plesiomorphic, found in Ceratodon, Polytrichum, Timmia and Ptychomitrium but usually absent in Encalypta; absence of a central strand is, however, not clearly associated with reduction in the Pottiaceae.

4. A stem sclerodermis is clearly differentiated in Ceratodon and Polytrichum but not is so in Encalypta or Timmia (outer cortical cells are smaller and only weakly thickened); one might assume the condition of Polytrichum is plesiomorphic in association with the large size and complexity of the plant. The situation is variable in Ptychomitrium.

5. Lack of a stem hyalodermis is plesiomorphic, being absent in Ceratodon, Encalypta (occasionally present in patches), Polytrichum and Timmia, but present in Ptychomitrium.

6. Basal cells of the axillary hair being colored rather than hyaline (as is the remainder of the hair) is advanced; this is true for Ceratodon and Timmia, but not Polytrichum. In Encalypta (several species examined), the basal cells are brownish, but entirely hyaline hairs have been reported, Horton 1982). Ptychomitrium is variable in respect to this character.

7. Leaves variously broadly channeled or tubulose when dry is advanced, this being variable in Encalypta and in Timmia and not tubulose in Ceratodon, Polytrichum or Ptychomitrium. Again, the condition of the genus with largest plant size is taken as plesiomorphic.

8. The leaves of Polytrichum and Timmia are strongly spreading, and nearly squarrose when wet; the condition is plesiomorphic. Those of Ptychomitrium are less strongly differentiated in this respect.

9. Leaves becoming gradually larger on the stem is the plesiomorphic condition.

10. Polytrichum, Timmia, Ptychomitrium and Ceratodon have lanceolate leaves; the condition is plesiomorphic. The spathulate to ovate-lanceolate leaves of Encalypta are taken as apomorphic, and, as in the Tortula group of Pottiaceae, associated convergently with loss of the ventral stereid band and enlargement of upper laminal cells.

11. Leaves usually relatively long, 3.0 µm or more, is the condition with Polytrichum and Timmia, and larger species of Ptychomitrium, and is plesiomorphic. Encalypta leaves are likewise rather large.

12. Although Ceratodon has keeled leaves, Polytrichum, Timmia, Ptychomitrium and Encalypta have broadly channeled leaves, and the latter is the plesiomorphic condition.

13. Although Ceratodon (and many robust genera of Pottiaceae) have leaves narrowly grooved along the costa, Polytrichum, Timmia, Ptychomitrium and Encalypta have a ventrally rather flat upper leaf surface, which is the plesiomorphic state.

14. Type of marginal flexion is a difficult character to polarize satisfactorily but is taxonomically critical. The upper leaf margins of Polytrichum, Timmia, Ptychomitrium, Diphyscium and the Dicranaceae in general are plane to incurved above (like those of Trichostomum in the Pottiaceae), those of Ceratodon are recurved, those of Grimmiaceae plane to recurved. Encalypta has both plane and recurved margins. Both incurved and recurved leaf margins are found in the Pottiaceae. If such flexion were equivalent evolutionarily (e.g. both providing marginal stiffening), then both directions of marginal recurvature would be apomorphic. Infolded margins, however, provide additional protection in arid environments, and this indicates an advanced condition. The state for Polytrichum, however, is taken as plesiomorphic with respect to the Pottiaceae.

15. The upper margins of Polytrichum, Timmia, Ptychomitrium and some species of Diphyscium are commonly strongly and distantly toothed, and those of Ceratodon are denticulate near the apex; Encalypta has entire margins. Robust species in the Pottiaceae commonly have dentate margins, and, given that robustness is here taken as plesiomorphic, the clearly dentate condition is considered likewise plesiomorphic.

16. The marginal ornamentation of Polytrichum, Timmia, Ptychomitrium, Encalypta, Bryobartramia and Ceratodon is never of denticulation restricted to the upper portion of the leaf base; leaf margins not denticulate only below is plesiomorphic. Molendoa is occasionally denticulate at the top of the leaf sheath margin while Eucladium is nearly always so.

17. Polytrichum, Timmia, Encalypta and Ceratodon lack bistratose leaf borders, but these are common in Ptychomitrium and Diphyscium; the unistratose margin is considered here plesiomorphic.

18. Cells of leaf margins similar to those of the medial leaf is the plesiomorphic condition.

19. Acute leaf apices are plesiomorphic; the apices are obtusely acute to rounded in Encalypta, but this is correlated with an apomorphic broadening of leaves and loss of ventral stereid band.

20. The cucullate leaf apex is an apomorphic character.

21. While Ptychomitrium and Ceratodon have a merely ovate leaf base, the leaf base of Polytrichum and Timmia sheathes the stem and has “shoulders,” the latter being the plesiomorphic state. The leaf base of Encalypta is occasionally differentiated in shape, but this is usually masked by the broadened distal portion of the leaf.

22. A percurrent costa is plesiomorphic.

23. Polytrichum, Timmia, Ptychomitrium and Encalypta have quadrate to very short-rectangular ventral costal cells, while Ceratodon has elongate ventral costal cells; the former is the plesiomorphic state.

24. Polytrichum and Timmia have a broad costa commonly more than 10 ventral cells across, which is the plesiomorphic state. The costa of Encalypta is 6–8 ventral cells in breadth, while Diphyscium commonly is 15 or more costal ventral cells across. Ptychomitrium, however, has a narrower costa.

25. The costal section of Timmia is elliptical, with the ventral surface usually distinctly convex, similar to that of Encalypta; Ceratodon and Polytrichum have a reniform costal section, the latter shape is probably plesiomorphic. The costal section of Ptychomitrium is semicircular and is probably derived.

26. Two stereid bands are present in Polytrichum, Timmia, Ptychomitrium and Ceratodon, which is the plesiomorphic character. Diphyscium commonly has two stereid bands while Encalypta has only one.

27. The ventral stereid band being smaller than the dorsal is the plesiomorphic state.

28. Polytrichum, Timmia, Ptychomitrium and Ceratodon have reniform, strongly flattened ventral stereid bands. The same is the case with Encalypta and Diphyscium.

29. Ventral costal epidermis being present is the plesiomorphic state. The lack of this is also rare in the Pottiaceae.

30. Dorsal costal epidermis being present is the plesiomorphic state; it is commonly absent in Encalypta, and is rare in Pottiaceae. Perhaps the similar Syntrichia, for which the lack of a dorsal costal epidermis is diagnostic, is an example of convergent evolution with Encalypta.

31. Polytrichum and Timmia usually have more than six guide cells (Brassard 1979 illustrates only six for Timmia); Ptychomitrium and Ceratodon have 2–6 guide cells, and Encalypta 6–8; a large number of guide cells is the plesiomorphic state.

32. A single layer of guide cells is the plesiomorphic state; Encalypta commonly has more than one; this is rare in Pottiaceae.

33. A hydroid strand (occasionally multiple) is present in Polytrichum, Timmia and Ceratodon and is the plesiomorphic state; a hydroid strand is variably present in Encalypta and absent in Ptychomitrium.

34. Although the ventral surface of the costa of both Polytrichum and Timmia is distinctly convex, it does not constitute a pad of cells (the longitudinal lamellae of Polytrichum are not considered a pad). Lack of a bulging pad of cells is the plesiomorphic state.

35. Ventral outgrowths absent or at least not of filaments is plesiomorphic; the presence of lamellae in Polytrichum is apparently advanced and is only matched in the Pottiaceae by Pterygoneurum.

36. The upper laminal cells of Polytrichum, Timmia and Ptychomitrium are rather small, ca. 9–14 µm in width, while those of Ceratodon are somewhat wider, and those of Encalypta 7–18 µm in width; the first state is plesiomorphic.

37. A short length to width ratio is plesiomorphic.

38. Upper laminal cells with thin to evenly thickened walls is the plesiomorphic state.

39. The upper laminal cells of Ceratodon, Polytrichum and Ptychomitrium are weakly convex and those of Encalypta strongly convex on both superficial surfaces (occasionally somewhat more bulging ventrally than dorsally in Encalypta), and those of Timmia are ventrally strongly mamillose and dorsally nearly flat (except T. sibirica, in which this difference is both poorly developed and masked by dense papillae). An areolation similar to that of Timmia is present in a far larger number of genera of the Pottiaceae than previously recognized (though often masked by papillae). The Calymperaceae (Pottiales) commonly has ventrally bulging upper laminal cells, which is probably the plesiomorphic condition for the Pottiaceae.

40. The unistratose leaf condition is plesiomorphic, though variable in Polytrichum and Ptychomitrium.

41. The superficial cell walls of the upper leaf being of equal thickness on both sides of the leaf is plesiomorphic. Although the dorsal cell walls of the leaf are commonly thicker than the ventral in the lower portion of the leaves of Timmia, the ventral and dorsal walls are of similar thickness in the majority of the limb.

42. The leaves of Ceratodon, Ptychomitrium and Polytrichum lack papillae, those of Encalypta are papillose, and those of Timmia are variously papillose or smooth. Inasmuch as most taxa in the Pottiaceae, including all robust, morphologically complex taxa of Pottiaceae (excepting Streptopogon), have papillose upper leaf cells, the papillose condition is presumed plesiomorphic and that of Polytrichum is advanced.

43. The papillae of Timmia are coarse and bifid, and those of Encalypta are generally well developed and bi- or trifid. The bifid to multifid state is plesiomorphic. None of the taxa was always capitulate or columniform.

44. Both Timmia and Encalypta have 2–4 papillae per lumen, the plesiomorphic condition. Polytrichum is scored, however, as characteristic not present.

45. The basal cells of Polytrichum, Ptychomitrium and Timmia are differentiated straight across the leaf base, thus being the plesiomorphic condition. They are poorly differentiated in Ceratodon and differentiated straight across or rising higher medially in Encalypta.

46. Propagula are unknown in Polytrichum, Ptychomitrium and Timmia, and are axillary and filamentous in both Ceratodon and Encalypta. The former state is the plesiomorphic condition.

47–51. Not polarized.

52. Ceratodon and Polytrichum are dioicous, Encalypta is largely autoicous but occasionally dioicous, and Timmia is largely dioicous but also monoicous. Ptychomitrium is monoicous. Monoicy, being associated with reduction in the Pottiaceae, is here regarded as apotypic (but cf. discussion of Stark and Castetter 1987, p. 195, who find no support for the hypothesis that monoicy is generally favored in arid lands).

53. The terminal perichaetium is the plesiotypic condition.

54. Although the perichaetial leaves are somewhat differentiated in Ceratodon, in Polytrichum, Ptychomitrium, Timmia and Encalypta they are little differentiated, which is considered here the plesiomorphic state.

55. An elongate seta is the plesiomorphic state.

56. The seta is twisted clockwise in Polytrichum, Ptychomitrium, Timmia and Ceratodon. In Encalypta it is twisted counterclockwise. The former is taken as plesiomorphic.

57. The thecae of both Polytrichum, Timmia and Ceratodon range from 2.5 to 3.0 µm in length, which is taken to be the plesiomorphic condition. The measurements for Encalypta are 1–3 µm, probably associated with reduction.

58. An ovoid to cylindrical capsule is the plesiomorphic state.

59. The stegocarpous condition is plesiomorphic.

60. Smooth capsule walls is the plesiomorphic state.

61. Evenly thickened superficial exothecial cell walls is the plesiomorphic condition.

62. Capsules stegocarpous is the plesiomorphic condition.

63. Stomates present is the plesiomorphic state.

64. The annulus is of vesiculose cells in Ptychomitrium, Timmia, Encalypta and Ceratodon, but is weakly developed in Polytrichaceae; the latter is probably the plesiomorphic state for the Pottiaceae.

65. Peristome teeth present is the plesiomorphic state for the Pottiaceae.

66. There are 64 inner peristome rami in Timmia, 16 of the homologous equivalent in Encalypta and Ptychomitrium, and 16 pairs of teeth fused at the joints in Ceratodon. Inasmuch as there are clear reduction series in certain genera of the Pottiaceae beginning with species with 32 similar rami, this latter condition is taken as plesiomorphic. Peristome teeth characters are scored as character not present in Polytrichum.

67. The ornamentation of the teeth of Timmia and Encalypta (endostomes) and of Ptychomitrium and Ceratodon is papillose to weakly spiculose in the first two and strongly spiculose in the last two. Ridged, striate or smooth are derived states.

68. Although the peristome teeth of Ptychomitrium, Timmia, Encalypta and Ceratodon are straight, having twisted peristome teeth is a major, unique character state of the Pottiaceae, and occurs in morphologically disparate intrafamilial groups; it is assumed to have been a feature of the immediate ancestry of the Pottiaceae and is here taken as plesiomorphic.

69. Peristome teeth, when twisted, wind mostly counterclockwise in the Pottiaceae, rarely clockwise. Ptychomitrium, Timmia, Encalypta and Ceratodon have straight teeth, while Ditrichum tortipes (Ditrichaceae) has its peristome and cells of the operculum clearly twisted counterclockwise. Since the last taxon may not represent a sister group but may instead be derived from Barbula sect. Hydrogonium, there is no good outgroup indication of the state of the hypothetical ancestor of the Pottiaceae. A counterclockwise twist is considered plesiomorphic based on ingroup comparisons: twisted peristomes in various major groups of the Pottiaceae are nearly all wound counterclockwise, and parallel derivation from a clockwise ancestor is far less probable than the occasional reversal.

70. Calyptrae are smooth in Ptychomitrium, Timmia and Ceratodon, which is the plesiomorphic state, but variously smooth, papillose or prorulose in Encalypta. This character is scored as “not smooth” for Polytrichum.

71. The calyptrae of Polytrichum and Timmia are generally 5–6 µm in length while those of Ptychomitrium and Ceratodon are reduced in size; the former is the plesiomorphic condition. Those of Encalypta are 2–10 µm in length.

72. The spores of Timmia are commonly 12–20 µm in diameter, those of Ceratodon are mostly 11–15 µm in diameter, and those of Encalypta 7–80 µm in diameter. Because larger spore size is generally associated with gametophytic reduction in the Pottiaceae, the smallest spore size state, also typical of Polytrichum, is taken as plesiomorphic.

73. Ceratodon is yellow in KOH; Encalypta is KOH yellow in the upper leaf but the basal cells react red, and mature leaves become KOH red or orange above; Buxbaumia, Diphyscium and Polytrichum leaves are red in KOH. Ptychomitrium is variable in KOH reactions. The upper lamina or upper (distal on the stem) leaves of Timmia in KOH are either yellow, orange, colorless, or faintly pink above (in T. austriaca Hedw.—walls were examined at high magnification under microscope to distinguish the bright yellow-green of the cell contents), occasionally with medial patches of brick-red blush, occasionally intensely brick-red at damaged portions of the leaves; the leaf bases and costae are generally a deep, clear yellow with large brick-red blotches. The botchy condition is similar to that of certain Tortula and Crossidium species, which are here considered essentially yellow in KOH because most species have strongly KOH yellow upper laminae of both young and mature leaves. Tortula (as emended here) and Crossidium species do not have leaves entirely with walls pink or red. The upper laminal cells of the more mature leaves (lower on the stem) of Timmia species, generally, have distinctly pink walls throughout; the mature leaf has much the color response as have those of Bryoerythrophyllum, here considered essentially red in KOH. Some species of Bryoerythrophyllum (cf. treatment of that genus) have KOH yellow young leaves but a typically red reaction of more mature leaves. Timmia has an essentially red color response of the upper laminae to KOH, which is here considered the plesiomorphic character state for the Pottiaceae.

74. The mitrate calyptra is characteristic only of reduced taxa in the Pottiaceae (excepting Streptopogon, which because of its evident lack of characters may be derived from highly reduced ancestors, cf. Cladogram 14, with little subsequent elaboration except in stature), and is here considered apomorphic. Ptychomitrium has a mitrate calyptra. The inflated campanulate calyptra typical of the Encalyptaceae is probably an elaboration of the mitrate type.