The genus Glonium Muhl.
Cont. Lab. Plant Disease Sci. Fac. Agric. Gifu Univ.101 (1813).

By Eric W.A. Boehm

 

 = Solenarium Spreng., Syst. veg. 4(1): 376, 414 (1827).
= Psiloglonium Höhn., Annls. mycol. 16(1): 149 (1918).

The genus Glonium is characterised by modified hysterothecia, progressively dichotomously branched, laterally anastomosed along their length to form radiating flabelliform or pseudo-stellate composites, usually seated upon a conspicuous brown felt-like subiculum, sometimes borne in a stroma (Zogg 1962). Hysterothecia in vertical section globose to obovoid, typically with a thick, three-layered peridium, but fragile, unlike the robust peridium of the Hysteriaceae. Luttrell (1953) described the development of the ascocarp in the type species, G. stellatum Muhl. as composed of small pseudoparenchymatous cells, the outer layer heavily encrusted with pigment and often longitudinally striate on the surface, the middle layer lighter in pigmentation and the inner layer distinctly thin-walled, pallid and compressed. The hamathecium consisted of persistent narrow cellular pseudoparaphyses, often borne in a gel matrix, with tips darkened or branched at maturity. Bitunicate asci are borne in a basal layer and at maturity are typically clavate to cylindric, bearing eight ascospores, overlapping biseriate; ascospores ranging from hyaline to pale yellow, 1-septate, conspicuously constricted at the septum, fusoid in outline, with at least one end, often both, acuminate, and showing bipolar asymmetry.

Zogg (1962) listed three species that he grouped together in his key, that later formed the basis for the Gloniaceae (Boehm et al. 2009). These are the type species, G. stellatum (Fig. 12A-E), G. graphicum (Fr.) Duby, and G. compactum Kern, the latter associated with both subicula and stroma. To these three species, we can add the recently described saxicolous, terricolous and lignicolous G. circumserpens (Nyl.) Kantvilas & Coppins (Fig. 12F-H) from Tasmania (Kantvilas & Coppins 1997). Although von Höhnel (1918) and Petrak (1923a) stressed the importance of subiculum as a synapomorphic character state, Zogg (1962) noted that G. graphicum may or may not be associated with a subiculum. This, combined with the observation that P. lineare may also on occasion be associated with subiculum, led Zogg not to accept the genus Psiloglonium. Data presented here and elsewhere (Boehm et al. 2009), however, indicate that the synapomorphic character state is not subicula per se, but the ascomata, which are modified hysterothecia that are progressively dichotomously branched, to form radiating pseudo-stellate composites. This is most pronounced in G. stellatum and G. circumserpens, but may also be found to a lesser extent in G. graphicum (Zogg 1962). One distinguishing feature that separates G. stellatum from G. circumserpens is that, although both are associated with subicula, in the former this extends as a wide margin in front of the developing hysterothecia (Fig. 12 A-C), whereas in G. circumserpens (Fig. F-G) the subicula is only associated with the under surface of the hysterothecia, closely appressed to the substrate, with only minor deviations from the long axis of the fruitbody.

In Boehm et al. (2009b) four isolates were surveyed for the Gloniaceae. Two of G. stellatum, from Michigan (CBS 207.34) and Tennessee (ANM 32), the United States, and two of G. circumserpens, recently isolated from wood (CBS 123342 / BPI 878738) and dolerite stone (CBS 123343 / BPI 878739) from Tasmania. Molecular data indicate that all four isolates are closely related. Surprisingly, this clade also includes multiple isolates of Cenococcum geophilum, an ecologically important ectomycorrhizal fungus with a global distribution and a wide host range, but with no known teleomorph (LoBuglio et al. 1996; see also Schoch et al. 2009c).

 

Key to the species of Glonium

 

1. Hysterothecia associated and seated upon a thin crust-like stroma, or arising from within a stromal crust; stroma itself seated on subiculum; didymospores spindle-shaped with the upper cell slightly swollen and larger than the lower cell, measuring 24-28 x 5-6 μm; Africa → Glonium compactum Kern

1. Hysterothecia not associated with stroma → 2

 

2. Hysterothecia somewhat branched, irregular, "graphoid"; without well-developed subiculum; didymospores oblong to spindle-shaped; upper cell pear-shaped, constricted at septum; both ends acuminate, measuring (13-)15-18(-21) x (3-)5-6 μm; on Pinus, Juniperus, Europe → Glonium graphicum (Fries) Duby

2. Hysterothecia in mature specimens highly bifurcated, closely appressed to the substrate, dichotomously branched to form irregular creeping masses; usually seated upon or sitting behind a front of well-developed brown to black subiculum → 3

 

3. Didymospores hyaline, constricted at the septum, apices pointed, measuring (15-)16-17 x 6-7 μm; on soil (terricolous) or rock (saxicolous), or lignicolous; Tasmania → Glonium circumserpens (Nyl.) Kantvilas & Coppins

3. Didymospores oblong to spindle-shaped; upper cell pear-shaped, constricted at septum; both ends acuminate, measuring (18-)21-26(-28) x (4-)5-6(-7) μm; cosmopolitan .→ Glonium stellatum Mühl.