This layer extends into the subtending hypha. When adherent to L3, it cannot be seen. In some spores it breaks away completely from the spore wall, and it has a small protrusion where it was attached to the subtending hyphal wall . The subtending hypha has a tendency to break off at the spore base and thus go undetected. Innermost sublayer of L3 of the spore wall occludes the hypha lumen, or a thin septum forms from L3.
Vesicles are rare, and then only sporadically distributed.
Infection units often overlap so that there are long, continuous regions of mycorrhizal colonization. Hyaline and mucilaginous in all three species, but it is most darkly dextrinoid in G. clarum and lightest in G. claroideum . Hyaline, degrades from spores of G. claroideum and G. luteum , but is permanent and much thicker in G. clarum . The greater thickness of this layer in G. luteum accounts for the darker yellow appearance of many spores in comparison to those of G. claroideum . Only present in spores of G. luteum and G. claroideum , with similar structure and position in the lumen of the subtending hypha.