Sexual reproduction, life history, and early development in culture of the Antarctic brown alga Himantothallus grandifolius (Desmarestiales, Phaeophyceae)*

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Abstract
The life history and early development of the sporophyte of Himantothallus grandifolius is reported. Unilocular sporangia are borne terminally on two-celled stalks interspersed with paraphyses. Meiospores develop into dioecious microscopic gametophytes. Male gametophytes have relatively small cells with few chloroplasts, cells of female gametophytes are larger and contain numerous chloroplasts. Oogonia and eggs, or antheridia each with one single spermatozoid are formed in short days. Sporophytes develop from fertilized eggs or parthenogenetically. At first they are uniseriate with an intercalary meristem. Subsequently laterals are formed in pairs, some of which develop basal intercalary meristems and eventually form lateral blades. The terminal blade originates from the main axis. In juvenile blades a central cavity is formed which is later filled with different types of cortical cells. The life history of H. grandifolius and in particular the character of the gametophytes is typical of the order Desmarestiales, confirming the placement of the species in this order.