Cheilolejeunea evansii (M. S. Taylor) R. M. Schuster

Distribution

Endemic to southeastern North America. U.S.A. Alabama, Georgia, North Carolina, South Carolina.

Habitat

A species of low elevation reaching 2200-2300 ft in Whitewater River gorge, North Carolina (Schuster 1980); most collections made in the last 20 years are from below 2000 ft and are from South Carolina and north Alabama. C. evansii occurs in hardwood forests usually containing Tsuga canadensis and sometimes Pinus strobus, often in close proximity to streams in ravines but also considerably upslope in drier conditions.

The following is a partial list of associated bryophytes from collections made in the last 20 years:   Cololejeunea biddlecomiae, Drepanolejeunea appalachiana, Frullania eboracensis, Frullania ericoides, Harpalejeunea ovata ssp. integra, Lejeunea laetivirens, Lejeunea ruthii, Lejeunea ulicina, Leucolejeunea clypeata, Metzgeria sp., Radula cf. australis, Radula obconica, Rectolejeunea maxonii, and the mosses Fissidens subbasilaris, Leucodon sp., and Schlotheimia rugifolia.

The following is a list of phorophytes with the number of collections in parentheses based on recent collections through 2016: Carya (7), Fraxinus (4), Ilex opaca (1), Liquidambar styraciflua (8), Liriodendron tulipifera (10), Nyssa sylvatica (14), Quercus alba (12), Q. coccinea (1), Q. falcata (1), Q. montana (5), Q. rubra (1), Q. velutina (1), and "red oak" (3). The above list is lengthened with the addition of Acer rubrum included in Schuster (1980).

Bark supporting C. evansii is frequently colonized, at least in small patches, by nearly black, filamentous Cyanophyta indicative of a microhabitat that experiences periodic desiccation in an otherwise usually humid atmosphere. In deeply shaded gorges the species occurs on bark that seems to be prone to desiccation and may receive bright light at least during part of the day. Sparse shoots of Fissidens subbasilaris often co-occur in what appears to be dryer parts of the tree trunk. Here the microhabitat seems to be at the limit of F. subbasilaris's tolerance and the limit of other bryophytes such as Radula obconica. R. obconica is frequently found intimately associated with C. evansii but is is never in full vigor.

As a field character to use when deciding where to lean in with a hand lens for a closer look, bark with seemingly sparse bryophyte coverage, or bark darkened with Cyanophyta, is often profitable.

Brief Description and Tips for Identification

Shoot width: to just over 0.5 mm wide, usually smaller.  Color: olive green.  Cell walls in leaf lobe: with large trigones and lacking intermediate thickenings.  Oil bodies in leaf lobe large and coarsely segmented; mostly 2 per cell but a few cells may have up to 5.   Lobules: inflated, the distal end of the lobule with mouth directed slightly to strongly upwards (towards the shoot apex); juncture at distal end of keel and the free lobe distinctly notched.  Underleaves: bilobed.

Monoicous. Usually sterile; sexual branches rarely found

Cheilolejeunea evansii often occurs admixed with a wide variety of other liverworts, especially other small Lejeuneaceae. Color can be very helpful (most other regional Lejeuneaceae lack the olive green color), but at times forms of other leafy liverworts can be easily confused in the field. Small forms of Radula obconica may be confused with C. evansii in the field. More challenging when first gaining a proper field eye is Harpalejeunea ovata ssp. integra which may be similarly colored and also possesses as distinct notch between the keel and the free lobe. The lack of underleaves in R. obconica and the broadly rounded underleaf lobe apices and more sharply pointed leaf lobe apices of H. ovata ssp. integra quickly distinguish these in the lab.

Salient Features

• Olive green color
• Trigones large in cells of dorsal leaf lobe
• Oil bodies large and coarsely segmented; mostly 2 per cell
• Underleaf bilobed; lobe apices pointed, not rounded
• Consistently on bark of trees

References

Schuster, R.M. 1980. The Hepaticae and Anthocerotae of North America East of the Hundredth Meridian. Volume IV. Columbia University Press, New York

Thiers, B. M. 2016. Lejeuneaceae. Bryophyte Flora of North America, Provisional Publication.