The origin of the forms described in these web pages is uncertain; they have been described as being of fungal origin (Wood and Elsik, 1999; Elsik, 1999; Visscher et al., 1996) and of possible algal origin (Krassilov et al., 1999). In view of this uncertainty a new terminology independent of mycology and phycology is adopted. The new terms suggested are given below (see also Figure 1). For details of the references quoted see the references page.

• Cell: the main unit of chains; usually hollow and cylindrical, but may be Y-shaped, ovoid or spherical.
• Terminal rim:
the darkened, slightly protuberant annular thickening usually present at the termini or opposite margins of the cell.

• Terminal plane:
the usually circular or rectangular area enclosed by the terminal rim, which is perpendicular in orientation to the long axis of the cell.

• Inner body:
the thin-walled body, internal to the cell, that normally mimics the overall shape of the cell but which may be of various shapes depending on the extent of its shrinkage.

Figure 1 Terminology

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