Plants of Voyria truncata, morphologically and anatomically most similar to its autotrophic relatives, also show a similar AM morphology. The advanced character of this mycorrhiza, however, manifests in the increased intensity of fungal infestations of the root, the fast degeneration of the hyphal coils within 15 cell passages and, most important, the missing arbuscles. Since fungal haustoria (arbuscles) in roots of achlorophyllous host are of questionable function, their missing is interpreted as a logical consequence of progression.
Voyria tenella, morphologically and anatomically one of the most advanced species in the genus, exhibit an entirely different course of growth of its root fungus. Root penetrating hyphae initially grow directly through the multilayered cortex parenchyma towards the longitudinally elongated cells of the 1-2 innermost cortex layers outside the endodermis.There, the hyphae proceed along the central cylinder. Hyphal branches subsequently colonize the root cortex from the inside. Leaving the inner cortex layers, however, the hyphae start to coil, swell up and eventually collapse. This unique pattern of mycorrhiza is interpreted as an intraradical fungus-garden. By this means, a sustained benefit of the fungal penetrations is achieved, considered to be a substantial progress in taking advantage of the mycorrhiza.
Since the mycorrhiza of V. tenella is an AM too, our present notion of host 'influence' on the morphology of its endophyte has to be reappraised. In V. tenella it attains a yet unknown quality.