Didymium atrichum Henney & Alexop.

Baba, Hayri, Gündoğdu, Fatma & Sevindik, Mustafa, 2021, Myxomycetes biodiversity in Gaziantep Province (Turkey) with four new records, Phytotaxa 478 (1), pp. 105-118 : 109-110

Didymium atrichum Henney & Alexop. ( Fig. 4 )

Sporocarps sessile, globose to plasmodiocarpous, scattered or clustered, 80–250 µm diam.; hypothallus conspicuous, gelatinous at first, slightly elevated when dry, sometimes resembling a short stalk; peridium membranous, sprinkled or covered with lime crystals; columella mostly absent, but sometimes rudimentary and then calcareous; capillitium absent; spore-mass black, spores mostly globose to subglobose, dark brown, 10–11 µm diam., spinulose or faintly reticulate under oil immersion, but conspicuously reticulate by SEM; phaneroplasmodium minute, milky white.

Comments:— In some sporangia of D. atrichum a calcareous mass at the base suggests a rudimentary columella reminiscent of that found sometimes in D. trachysporum . This and the fact that the latter species often has a scanty capillitium and spores on which the warts are often arranged in lines to form an inconspicuous reticulation, suggests a possible relationship between the two species. It is closer to that of D. trachysporum in that both these species have lime crystals united laterally into flattened discs ( Henney et al. 1980).

D. atrichum has a very restricted distribution, since it was known previously only from North America and Africa. Because of the presence of crystalline lime on its peridium, this species is placed in the genus Didymium . The sporangia are produced either singly or in heaped clusters resembling pseudoaethalia, the often clustered sessile sporangia. The most distinctive taxonomic characters of this species are its rather small sessile sporophores 100–300 μm diam., the absence of a capillitium and spores that are faintly reticulate. The spores, using light microscopy appear minutely verrucose or faintly reticulate, but the scanning electron microscope reveals a conspicuous, sometimes broken reticulation ( Henney et al. 1980, Stephenson et al. 2019).

Specimens examined:— Şahinbey, on dead leaves of Quercus sp. , Baba 68, Oğuzeli, on dry leaves of Quercus sp. , Baba 89.

World distribution:— Africa, USA.

Figures

FIGURE 4. Didymium atrichum. a. Sporocarps. b, c. Spores and lime crystals. d. Spore.