It is not even analagous to a germinal wall even though similar in appearance because it has no role in germination processes. Since it originates as part of the subtending hypha, it is considered as the innermost layer of the spore wall. It is not considered as a sublayer of L3 because it consistently separates to varying degrees from the spore wall. L1 and L2 usually absent from the surface of mature spores. In many spores, the hyphal wall is so fragile that it breaks from the spore and cannot be seen.
Branch hyphae from the main trunk of the arbuscule narrow incrementally to numerous fine tips.
Intraradical hyphae of a mycorrhiza also stain darkly in trypan blue. Some hyphae will have the appearance of projections, but they often are remnants of the trunk hyphae of intracellular arbuscules. Vesicle development is sporadic and patchy, rarely abundant in any particular infection unit. Many mycorrhizae consist of few to no vesicles. Occurrence and abundance of vesicles may be as much an expression of environmental as genetic determinants.