This layer appears to be quite variable in its appearance among spores of the same accession and also between accessions. It is uncertain whether this layer just isn't being synthesized or it is just not detectable. Rarely present on the hypha of mature spores. The inner layer is concolorous with L3 of the spore wall, with sublayers adherent. These germ tubes branch extensively after emergence from the hypha.
Sporocarps are most dramatic in producing numerous infective hyphae.
They decline as colonization and sporulation increases. Vesicle production is very sporadic, with most isolated from each other. Abundance does not often increase that much as a mycorrhiza ages. Late in mycorrhizal development, roots contain mostly intraradical hyphae and sporadic arbuscules and vesicles. It may form in all spores, but be so thin in some that it is not detected.