Guide to Liverworts of Oregon: Conocephalum conicum (L.) Underw.
HOME SPECIES INDEX GENUS INDEX GLOSSARY
1a plants thallose > 2b chloroplasts numerous > 62b thallus tissue complex > 70b terrestrial > 72b pores differentiated > 73b gemmae absent > 75b trigones small or absent > 77b pores not stellate > 79b pores simple > 81a thallus large > Conocephalum
Synonym: None. Misapplied in North America: Conocephalum salebrosum Szweykowski, Buczkowska et Odrzykoski
Special Status: None.
Recognition: The large thallus with prominent alligator skin pattern is unmistakeable.
Flora of North America description:
FAMILY Plants thalloid, terrestrial, dull to shiny green, sometimes yellow-green, rarely purplish. Thallus with a broad midrib, upper surface prominently areolate, pores simple, cells surrounding pores thin-walled, domed; ventral scales present, 2-ranked, scale appendage reniform, often tinged with reddish purple. Sexual condition dioicous, antheridia in male disks on edge of thallus, archegonial receptacles stalked, originating from apical notch; carpocephalum a rounded cone, weakly lobed, one sporophyte per involucre, epidermis with a stomatal apparatus protruding into air space. Capsule lacking protection of pseudoperianth, spherical to obovoid or ellipsoidal, opening by 4--6 irregular valves. Elaters present. Spores greenish, thin-walled, delicately papillose, chlorophyllose, early becoming multicellular.
GENUS Thallus broad, to 20 cm long and 12 mm wide, with a narrow unicellular margin, upper surface prominently areolate, areolae roughly rhombic, demarcated by narrow groves; discrete air chambers one per areola, air chambers floor with chlorophyllose filaments having elongate, clear ends, upper epidermis one cell thick, underlying the photosynthetic layer are 2--4 layers of thin-walled, large cells; ventral tissue solid. Elaters 3(--5) spiral.
SPECIES Thallus often with a dark central strip of smaller areoles grading into larger aureoles arranged in curving rows across the upper surface, 5--8(--10) areolae between midrib and edge of thallus, epidermal surface cell walls not bulging, relatively level across thallus except where indented to form the grooves; stomatal apparatus in epidermis of carpocephalum with a dome composed of 2--3 rings of thick walled cells and a slender tube of 5--6 elongated cells protruding into the interior air chamber.
Distribution: On various substrates, usually with organic layer but sometimes on gravel, where wet most of the year; in riparian zone in western Oregon, mostly at middle and lower elevations.
Comments: Although this species is very common in the lowlands of western Oregon, it is rarely seen fertile. The species we have in the Pacific Northwest is a microspecies similar to, but not identical with, Conocephalum salebrosum (Szweykowski, et al., 2005). According to Miwa, et al. (2005) our plants belong to cryptic "species C," not formally named, which is restricted to Pacific North America. The type of Conocephalum conicum is cryptic "species L," confined to Europe. Cryptic "species S," Conocephalum salebrosum, is found widely in Europe and Asia but known in North America only from a single Colorado accession (Miwa, et al., 2009). Cryptic "species A," also unnamed, is restricted to eastern North America.
Clarity has come from more recent phylogenetic studies of rbcL sequences. The pioneering work by Miwa et al. (2009) showed that except for a single possible record of C. salebrosum in Colorado, neither C. salebrosum nor C. conicum occur in North America. Instead, they identified two cryptic species, which they designated Type A and Type C, the former mostly in the east and the other in the west. It is possible that future work with anatomical characters of fresh plants will distinguish A type from C type. Akiyama, H. and Odrzyoski, I.J. (2020) suggest A and C could be treated as one species. The rarity of sporophyte production makes naming species on this basis not generally useful. Paton (2022) mentions that no fertile plants of Conocephalum had been found in the British Isles at the time she was writing. An approach is detailed in an anatomical study of thallus and carpocephalum characters undertaken on material from Oregon by Wagner (2023). Further study is anticipated.
Extensive study shows the cryptic species cannot be determined morphologically from herbarium specimens. It does not seem wise to call any specimen Conocephalum salebrosum in a narrow sense unless it can be clearly defined both morphologically as well as biochemically. Given current knowledge, the oldest name that can be used in a broad sense is C. conicum. Eventually, it should be possible to circumscribe "Species C" sufficiently to warrant a formal name. For now, I recommend using C. conicum in a broad sense for the regional plants because it is definitely not C. salebrosum.
Conocephalum conicum - Cape Creek, Lincoln County, Oregon.
Conocephalum conicum - Cape Perpetua Campground, Lincoln County, Oregon.
Conocephalum conicum - Note absence of a darkened central strip of thallus. Slopes above McKenzie River near Vida, Lane County, Oregon.
Conocephalum conicum - Haida Gwai, British Columbia, Canada. Des Callaghan 2023
Conocephalum conicum - Bull Run Watershed, Oregon. Nick Otting 2018.
Conocephalum conicum - Northfield, Massachusetts. Charles Eisen iNaturalist 11673121.
Conocephalum conicum - Thallus sections, junction of dorsal groove. Goodman Creek, Lane Co., Oregon. DHW m1778a.
Conocephalum conicum - Thallus sections, middle and margin. - Goodman Creek, Lane Co., Oregon. DHW m1778a.
Conocephalum conicum - Thallus margin. - Goodman Creek, Lane Co., Oregon. DHW m1778a.
Conocephalum conicum - Thallus sections, junction of dorsal groove. Goodman Creek, Lane Co., Oregon. DHW m1778a.
Conocephalum conicum - Thallus sections, junction of dorsal groove. Goodman Creek, Lane Co., Oregon. DHW m1778a.
Conocephalum conicum - Thallus sections, junction of dorsal groove. Goodman Creek, Lane Co., Oregon. DHW m1778a.
Conocephalum conicum - Ventral Scale appendage. - Butte Creek Falls, Marion County, Oregon. DHW m1872.
Conocephalum conicum - Pegged rhizoids from lower surface. - Butte Creek Falls, Marion County, Oregon. DHW m1872.
Conocephalum conicum - Young carpocephalum. - Saddle Mountain, Clatsop Co., Oregon. Photo by Larry Rea.
Conocephalum conicum - Ventral view of carpocephalum, showing nearly mature sporangia. - Butte Creek Falls, Marion County, Oregon. DHW m1872.
Conocephalum conicum - Thick section through center of carpocephalum, stomatal apparatus location indicated by markers. - Butte Creek Falls, Marion County, Oregon. DHW m1872.
Conocephalum conicum - Stomatal apparatus in carpocephalum. - Butte Creek Falls, Marion County, Oregon. DHW m1872.
Conocephalum conicum - Stomatal apparatus in carpocephalum. - Butte Creek Falls, Marion County, Oregon. DHW m1872.
Conocephalum conicum - Stomatal apparatus in carpocephalum. - Butte Creek Falls, Marion County, Oregon. DHW m1872.