This description is a combination of information obtained from the protologue (Walker and Rhodes, 1981), type specimens, and universal patterns of morphological organization and structure in Glomaceae. A living culture of this species has never been obtained by INVAM.

Spores are borne singly in soil; globose, subglobose, irregular, or ellipsoid; (125-) 160 (-180) x (120-) 140 (-175) µm; dull yellow or yellow- or orange-brown in color.

The spore wall is composed of two distinct, separable layers (L1 and L2). The outer layer (L1) is hyaline, 0.5-2 µm thick, degrading and sloughing with age. There is no mention in the protologue of reaction in Melzer's reagent, but the authors' description of young spores as reacing pink to orange-red suggests that this layer is mucilagenous and reactive (like that of many other Glomus species). The inner layer (L2) is pale yellow and of near equal thickness to L1 (0.5-2 µm).

The subtending hypha is single; cylindrical, sometimes constricted or slightly flared toward the point of attachment, (3) 5-15 µm wide at the spore base. The hyphal wall consists of two layers continous with layers of the spore wall. The outer layer is very thin (< 0.7 µm thick) and usually sloughs; the inner layer is < 2 µm thick. The hyphal wall tends to shrivel as the spore ages, thus becoming difficult to see.

Occlusion: Often none is present so the hyphal lumen remains open; occasionally a bulging septum is formed 5-20 µm distal to the spore.

Germination: According to Walker and Rhodes (1981), spore germinate only by germ tube emerging directly through the spore wall. They did not observe regrowth of the subtending hypha, which is most unusual among species of Glomus.

Type specimens from Oregon State University do not match the description of G. albidum; rather their morphology is typical of G. intraradices.

REFERENCES

Walker, C. and L. H. Rhodes. 1981. Glomus albidus: a new species in the Endogonaceae. Mycotaxon 12:509-514.