Niebla and Vermilacinia (Ramalinaceae) from California and Baja California.  
Spjut, R.W., 1996. ISSN 0833-1475, 208 pp.  
Sida, Botanical Miscellany 14. Botanical Research Institute of Texas, Inc.

Bahía de San Quintín,
Spjut 10234, Mar 1988

San José Ranch between Punta Canoas and Punta Blanca,
Spjut & Marin 11386, Apr 1990

Puerto Catarina, Spjut
 & Marin 13016, Apr 1994

Puerto Catarina, Spjut
& Marin 13034, Apr 1994

Cerro Solo, BCN, Spjut &
Marin 9047, May 1985, isotype

San Andrés Ranch,
~100 km N of Guerrero Negro, Spjut & Marin 9888B, May 1985

Point Pederales, CA
Bratt 5589

     Niebla eburnea is identified primarily by its creamy (ivory)-glazed cortex, and also by its branches twisting more near apex and base than in the mid region, and by the key lichen substance, divaricatic acid.  It is common in California and the Channel Islands, appearing less frequent in Baja California, except around Bahía de San Quintín—where it may be commonly found in association with other Niebla species.

     The original (type) collection was from near Cerro Solo (between San Vicente and Colonet), and was part of sample submitted for antitumor and anti-HIV screening.  It was taken from a vertical rock face near ocean mist, along with separate samples of N. josecuervoi, Vermilacinia laevigata, and V. ceruchoides from the same rock.  Duplicates were later provided to the Lichen Exchange at ASU, in addition to distribution of types by the Smithsonian Institution to BCMEX and LA. 

     Thalli of N. eburnea at the type location are similar to those of N. cornea (sekikaic acid) at Morro Bay and in the Channel Islands by having mostly simple, apical dilated branches, and by branches uniformly blackened around the basal area.   The two species are best separated by chemistry; nevertheless, N. cornea may be recognized by the small clusters of cupular apothecia, usually four in number, near a branch apex, in contrast to solitary, lenticular apothecia in N. eburnea, often seen on short, thickened nodular branchlets along lower branch margins, but other thalli may be found with terminal apothecia as in the type.

     Occasional specimens of N. eburnea are difficult to distinguish from N. homalea (divaricatic acid) and N. disrupta (sekikaic acid).  These related species generally have narrower branches that twist frequently between the base and apex, and their cortex is glossy with frequent transverse cracks.  The problematic specimens have dilated segments in the mid region rather than near the apex as exemplified by Bratt 5591 from Point Pederales, CA (photo 10.3 in Spjut 1996). These are identified as N. eburnea by the branches appearing thicker near margins and/or apex, in contrast to wing-like margins of N. homalea.  Also, the cortex of N. eburnea often develops longitudinal creases instead of transverse cracks.

     Another related species, N. testudinaria, differs by the regular appearance of reticulate cortical ridges in which the branches appear more prismatic than sub-tubular; it occurs from California to Baja California Norte, especially in the Channel Islands, and is also on Isla Guadalupe and on Isla San Martín.