Afrothismia winkleri develops fleshy rhizomes, densely covered with small root tubercles, narrowing to filiform roots with age. The exclusively intracellular mycorrhiza fungus has distinct morphologies in different tissues of the plant. In the filiform root the hyphae grow straight and vesicles are borne on short hyphal stalks. The straight hyphae are present in the epidermis of the root tubercles, but change to loosely coiled and swollen hyphae in the rhizome tissue. No penetration from epidermis to root cortex was found. From the rhizome a separating cell layer permits only one or rarely two hyphal penetrations into the cortex of each root tubercle. The hyphae proceed apically within the root hypodermis in a spital row of distinctively coiled hyphae, branches of which colonize the inner root cortex. In the inner root cortex the hyphal coils degenerate to amorphous clumps. In order roots the cortex itself also deteriorates, but epidermis, hypodermis endodermis and central cylinder persist. The mycorrhizal pattern in A. winkleri is interpreted as an elaborate exploitation system wherby the fungus provides carbon and nutrients to the plant and, simultaneously but spatially distinct, its hyphae are used to translocate and store the matter within the plant. Several features indicate that the endophyte is an arbuscular mycorrhizal fungus. [ABSTRACT FROM AUTHOR]