BFNA Title: Zygodon
Author: D. H. Vitt  
Date: October 6, 2003
Edit Level: R Brum+
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden
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Zygodon - Orthotrichaceae


9.  Zygodon Hooker & Taylor, Musc. Brit. 70. 1818 · [yoked (or paired teeth), referring to the 16 peristome teeth that initially are joined in pairs in some of the species]


                                                                                                                               Dale H. Vitt


Plants to 10 cm.  Stem leaves loosely-erect and irregularly twisted or curved around stem, sometimes undulate when dry, erect-spreading to squarrose-recurved when moist, oblong-lanceolate to linear-lanceolate, 0.5--2.0 mm, acute, usually apiculate, keeled, decurrent; margins entire or ± denticulate near apex; costa percurrent, ending near apex, or rarely excurrent; distal laminal cells 4--14 µm wide, densely pluripapillose, smooth or with 3--6 small, clavate papillae per cell, somewhat to very thick-walled; basal laminal cells usually yellowish, subquadrate to rectangular; gemmae elliptic to cylindric or fusiform, 4 to many celled, axillary.  Sexual condition dioicous, autoicous, or synoicous, rarely with sporophytes.  Seta 3--13 mm. Capsule elliptic-oblong to fusiform, 1--2 mm, strongly 8-ribbed along ± the entire length, not constricted beneath mouth; peristome double, single, or lacking; endostome segments 8 or 16, when present; exostome teeth 8 or 16 partially united into 8 pairs.  Spores 11--22 µm.


Species ca. 90 (5 species in the flora): North and South America; Europe; Asia, Africa, Australia, Pacific Islands (New Zealand).


Sporophytes are rarely produced in many species of Zygodon, and taxa are delimited on characters derived exclusively from the gametophyte.  Largely pan-tropical with several widespread temperate species.  None of the species is found farther north than 60° N latitude.



1.  Distal leaf cells smooth . . . 3. Zygodon menziesii

1.  Distal leaf cells papillose.

2.  Leaves squarrose-recurved, bluntly acute; distal leaf cells 4--9 µm, very thick-walled; gemmae never present . . . 2. Zygodon gracilis

2.  Leaves spreading to ± recurved, sharply acute-apiculate; distal leaf cells 5--14 µm, moderately thick-walled; gemmae always present.

3. Abaxial surface of costa covered by quadrate, papillose cells only at extreme apex; synoicous . . . 4. Zygodon reinwardtii

3.  Abaxial surface of costa covered by quadrate, papillose cells in distal 1/3 to 1/2 of leaf; dioicous.

4.  Gemmae fusiform-cylindric, never with transverse walls; distal leaf cells 9--14 µm wide . . . 1. Zygodon conoideus

4.  Gemmae clavate to ellipsoidal, with or without transverse walls; distal leaf cells 5--11 µm wide . . . 5. Zygodon viridissimus


1. Zygodon conoideus (Dickson) Hooker & Taylor, Musc. Brit. 71.  21.  1818


Bryum conoideum Dickson, Pl. Crypt. Brit. Fasc. 4: 9. 11 f. 2. 1801


Plants to 0.7 cm.  Stem leaves loosely erect and not contorted when dry, spreading to ± recurved when moist, 1--1.7 mm, oblong-lanceolate, broadly acute, with abrupt apiculus, usually ending in a long, clear cell; margins entire; costa ending near apex; distal laminal cells 9--14 µm wide, with 2--4 small, clavate papillae per cell, somewhat thick-walled; basal laminal cells pale yellow, subquadrate to short-rectangular; gemmae cylindric to fusiform. Sexual condition dioicous.  Sporophytes not known in North America.


Tree trunks, occasionally on dead branches; low elevations; N.S.; Mass.; Europe.


Zygodon conoideus is distinguished from Z. viridissimus by having wider, oblong-lanceolate leaves, larger leaf cells, and gemmae that have 4--7 horizontal, but no longitudinal septae.


2.  Zygodon gracilis Berkeley, Handb. Brit. Moss. 219.  1863


Plants to 5 cm.  Stem leaves erect-appressed, somewhat contorted and recurved when dry, wide-spreading to recurved-squarrose when moist, lanceolate to oblong-lanceolate, 1.4--2 mm, bluntly acute, margins sharply serrate near apex; costa prominent, usually excurrent or ending obscurely in tip, with distal 1/2 of abaxial side covered with papillose-quadrate cells; distal laminal cells 4--9 µm wide with 2--4 clavate papillae, very thick-walled, basal laminal cells elongate-rectangular to short-rectangular; gemmae not present.  Sexual condition dioicous.  Sporophytes not known in North America.


Restricted to calcareous rocks; alpine and subalpine regions; B.C.; Central America (Guatemala).


Zygodon gracilis is distinguished from other species of the genus in North America by squarrose-recurved leaves; absence of gemmae; bluntly acute leaves; and very thick-walled distal leaf cells.


3.  Zygodon menziesii (Schwaegrichen) Arnott, Mem. Soc. Linn. Paris 5: 233. 1827


Codonoblepharon menziesii Schwaegrichen, Spec. Musc. Suppl. 2(1): 142. 137. 1824; Zygodon drummondii Taylor


Plants 0.3--10 cm.  Stem leaves loosely incurved-twisted when dry, erect-spreading to spreading when moist, oblong, 1.2--1.8 mm, acute; margins entire; costa with abaxial side covered by quadrate papillose cells at apex; distal laminal cells 7--13 µm wide, smooth, somewhat thick-walled; basal laminal cells short-rectangular; gemmae fusiform to elliptic, transverse walls absent in North American material.  Sexual condition dioicous.  Sporophytes not know in North America.


Trees in the San Francisco area; Calif.; s South America; Australia; Pacific Islands (New Zealand).


The smooth leaf cells distinguish this species from all others of the genus in the area.  Here for simplicity I have retained it in Zygodon, but it probably belongs in a separate genus, Condonoblepharon.


4.  Zygodon reinwardtii (Hornschuch) Bruch, Schimper & W. Gümbel, Bryol. Eur. 3, fasc. 4 (Zygodon, p. 9).  1838


Syrrhopodon reinwardtii Hornschuch, Nov. Act. Ac. Leop. Car. 14(2): 700.  39.  1829; Zygodon reinwardtii var. subintegrifolius Malta



Plants to 2 cm.  Stem leaves irregularly-twisted or curved, loosely spiraled around stem and ± undulate when dry, spreading to wide-spreading, sometimes subsquarrose,  recurved when moist, oblong-lanceolate to broadly lanceolate, leaves 0.7--2 mm, sharply acute, usually with a 1 to many-celled apiculus, decurrent; margins entire to ± sharply serrulate near apex; costa slender, ending near apex; distal laminal cells 5--11 µm wide with 3--6 clavate papillae, somewhat thick-walled; basal laminal cells short-rectangular; gemmae clavate to elliptic.  Sexual condition synoicous or autoicous.  Spores 17--22 µm.


Trunks of trees; low elevations; B.C.; Alaska; Mexico; West Indies; Central America (Guatemala, Costa Rica, Panama); South America; Asia; Africa; Pacific Islands; Australia.


Identifying characteristics of this species include (1) leaves entire or ± serrulate at apex; (2) synoicous or autoicous; and (3) back of costa smooth, not covered with papillose, quadrate cells in distal 1/2 of leaf.  The serrulation of the distal leaf margins is highly variable, with some specimens having sharply serrulate margins (in the past placed in var. reinwardtii), while others have entire margins or margins with one or two small teeth (placed in var. subintegrifolius).  I doubt the value of taxonomically distinguishing thes plants.


5.  Zygodon viridissimus (Dickson) Bridel, Bryol. Univ. 1: 592.  1826


Bryum viridissimum Dickson; Pl. Crypt. Brit. Fasc. 4: 9. 10 f. 18. 1801


Plants to 2.3 cm.  Stem leaves loosely-erect and ± spirally twisted to somewhat contorted, sometimes falcate-secund in distal portions of stems when dry, erect-spreading to spreading when moist, oblong-lanceolate, lanceolate, or linear-lanceolate, 0.5--2 mm, acute, with gradual, 1--few celled apiculus, ± keeled below, decurrent; margins entire or with sharp, irregular teeth near apex, somewhat wavy; costa ending below apex with abaxial side covered with quadrate papillose cells only at apex; distal laminal cells 7--11 µm wide, with 2--4 clavate papillae, somewhat thick-walled; basal laminal cells pale-yellow, subquadrate to rectangular; gemmae clavate to elliptic.  Sexual condition dioicous.  Spores 11--15 µm.


Varieties at least 5 (4 in the flora); high elevations; widely scattered in the flora area, from Alberta. and Quebec south to Massachusetts and California; North and Central America; Europe; w Asia; Africa; Atlantic Islands (the Canaries).


Zygodon viridissimus in the flora includes Northern Hemisphere Zygodon phenotypes with (1) ovate to elliptic gemmae, (2) narrowly lanceolate, loosely erect leaves, (3) the abaxial surface of the costae in the distal 1/3--1/2 of the leaf covered with papillose, quadrate cells, (4) dioicous sexual conditions, and (5) rudimentary (or no) peristome.  The species is generally found on tree trunks and in crevices on vertical rock faces, usually at high elevations (up to 4000 m in western N. America).



1.  Leaves serrulate at apex.

2.  Gemmae without curved longitudinal septae; plants less than or equal to 5 mm. . 5a. Zygodon viridissimus var. A

2.  Gemmae with curved longitudinal septae; plants greater than or equal to 5 mm. . 5b. Zygodon viridissimus var. dentatus

1.  Leaves entire.

3.  Gemmae with longitudinal septae; leaves oblong-lanceolate to lanceolate. . . 5d. Zygodon viridissimus var. viridissimus

3.  Gemmae without longitudinal septae; leaves lanceolate to linear-lanceolate . . 5c. Zygodon viridissimus var. rupestris


5a.  Zygodon viridissimus var. A

Zygodon apiculatus Redfearn, Bryologist 70: 333.  1967


Plants 0.1--0.4 cm, dark-green to brownish.  Stem leaves oblong-lanceolate to oblong-ovate, 0.5--1.3 mm, acute and abruptly apiculate; margins irregularly serrulate at apex or sometimes entire; brood bodies elliptic to subcylindric, without longitudinal septae, of 3--5 cells.  Sporophyte not known.


Trunks of deciduous trees in dry oak-hickory climax zone; N.C., Mo. 


This variety is restricted to the southern Appalachians and Ozark Mountains. It differs from its closest relative, Z. viridissimus var. rupestris, by its small size and serrulate distal leaf margins.


5b.  Zygodon viridissimus var. dentatus (Juratzka) Limpricht in G. L. Rabenhorst, Deutschl. Crypt. fl. (4) 2: 12.  1890


Zygodon dentatus Juratzka, Laubmfl. Oest. Ungarn 190. 1882


Plants to 1.7 cm, light green.  Stem leaves ± twisted when dry, oblong-lanceolate to narrowly-lanceolate, 1--2 mm, acute, usually with  ± gradual apiculus; margins irregularly serrate near apex; brood bodies with longitudinal septae, septae curved, of 4--9 cells.  Sporophytes not known in North America.


Crevices in vertical rock faces; 3000 m; Ariz.; Europe.


This variety is distinguished by its robust plants, sharply toothed distal leaf margins, and abundant gemmae having curved longitudinal septae.  It has been found in the flora only in the White Mts. of Arizona.


5c.  Zygodon viridissimus var. rupestris Hartman, Handb. Skand. Fl. ed 5: 371. 1849


Plants to 2.3 cm, yellow-green, olive-green, or brownish.  Stem leaves linear-lanceolate to elongate-lanceolate, 1--2 mm; short-acuminate or apiculate apex of 1--3 cells; margins entire; brood bodies elliptic, without longitudinal septae, of 3--5 cells.  Sporophytes not found in North America.


Trunks of trees and on rocks; low to middle elevations; Alta., B.C., N.B., N.S., Ont., Que.; Ariz., Calif., Mass., Mich., N.Mex., N.Y., N.C., Oreg., Tenn., Va., Wash., Wis.; ne Mexico; Europe, n Asia; n Africa.


5d.  Zygodon viridissimus (Dickson) Bridel var. viridissimus


Plants to 1.5 cm, light-green to olive-green, usually with very little tomentum.  Stem leaves oblong-lanceolate to lanceolate, 1--2 mm, short-apiculate; margins entire; brood bodies with longitudinal septae, septae ± straight, of 5--10 cells.  Sporophytes not found in North America.


Trunks of trees, large, conglomerate boulders; low elevations; N.S., Que.; Europe.


This variety is distinguished by its entire leaves and gemmae with longitudinal septae.