SEM studies of fibrils formed from the synthesis of Usnea strigosa mycobiont with the photobiont Trebouxia erici revealed similarities with the natural lichen in terms of morphology and secondary compounds even though the extent of lichenization with the foreign alga was much less. Synthetic forms of an Antarctic cryptoendolithic lichen, which in its natural state does not form a thallus, showed the beginnings of thallus formation. We suggest that the endolithic lichen is a modification of an epilithic form and that the loss of thallus organization in the endolithic habitat is an environmental response and is not irreversible. Some evidence indicates that lichen photobionts have a heterotrophic nutrition in situ and that they may receive nutrients from their fungal partner.