Cymbella C.A. Agardh
Description
Frustules biraphid,
asymmetrical to the apical axis, symmetrical to the transapical axis. Dorsiventrality
slight (with some species approaching naviculoid symmetry) or pronounced. Raphe
centrally located or eccentric. Stigmata lacking or on the ventral side of the
central area. Distal raphe ends straight or deflected dorsally. Cells benthic,
free or in mucilage, or growing at the ends of mucilaginous stalks. Apical pore
fields at both poles or lacking.
The broad sense
of Cymbella embraced here (and in recent treatments of the genus, e.g.
Krammer 1982; Krammer and Lange-Bertalot 1986; Round et al. 1990), is probably
not a natural group of taxa. It contains everything that is not referred to
Encyonema or Reimeria. A natural group within Cymbella
contains those species with ventrally-placed stigmata, dorsally deflected external
distal raphe ends and apical pore fields.
Light Microscope Image(s)
Each image is accompanied by the genus and species, California Academy of Sciences slide number (ie. CAS 612010), location of the specimen on the slide, and dimension in microns.