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Sphaerostilbe repens gives rise to aggregated organs composed of aerial coremia and rhizomorphs which grow submerged in the medium. These two types of organ are structurally continuous. The sequence of events leading to organ differentiation under controlled laboratory conditions has been microscopically divided into four stages: 1. The vegetative phase which is characterized by a regular distribution of hyphae in culture media. 2. The aggregating phase in which a local cellular growth leads to the formation of a prosenchymatous mass. 3. The differentiating phase is distinguished by a parallel orientation of the hyphae in the middle of the aggregate. This is followed by an upward and downward growth of numerous hyphae giving rise to primordia of coremia and rhizomorphs respectively. At the periphery of the aggregate, cells become compact, isodiametric and vacuolated to produce the cortex of the rhizomorph, whereas in the middle of the organ, medulla in continuity with the coremium is filled with loosely woven and randomly oriented hyphae. 4. The elongating phase appears as an autonomous growth of organs which elongate by their apices. [ABSTRACT FROM AUTHOR]

Changes in the biochemical composition of isolated cell walls were analysed during the differentiation of coremia and rhizomorphs in Sphaerostilbe repens. Differentiation was accompanied by exclusively quantitative variations of the wall components: the content in carbohydrates, chitin and free amino sugars increased; on the contrary, amino acids, uronic acids, lipids and mineral substances decreased. Carbohydrates were composed of glucose, galactose and mannose; glucosamine was the main component of amino sugars. The predominant amino acid in the walls was cysteine the amount of which increased during hyphal aggregation, while quantities of the sixteen other determined amino acids decreased. Mineral matter was present in large quantities in the walls of the fungus, especially in vegetative mycelium. Iron, phosphorus and calcium were the most abundant elements. Possible relations between the variations in chemical composition of the wall and the capability of hyphae to aggregate are discussed. [ABSTRACT FROM AUTHOR]