GENERA starting with "g"


Geissleria 6

  1. Annulae present at poles
  2. Isolated punctum present or absent in the central area
  3. Valve elliptical or linear-elliptical with rounded or rostrate ends

Symmetrical biraphid - Geissleria valves are elliptical to linear-elliptical, becoming obtuse, broadly rounded or rostrate at the ends. The striae are comprised of fine lineolate areolae; aerolae 50-80 in 10 ┬Ám. Distinctive annulae are present at the poles. The annulae are comprised of one to four transapical striae that interrupt the typical striae. The raphe is straight and filiform, with straight proximal ends. Terminal raphe ends are...

Gomphoneis 14

  1. Valves clavate, symmetric to the apical axis
  2. Pseudoseptae present
  3. Longitudinal lines may be present
  4. Striae multiseriate

Asymmetrical biraphid - Gomphoneis valves are clavate in both valve and girdle view. Valves are symmetrical to the apical axis. Two distinct groups are currently included within the genus Gomphoneis. One group contains species (including G. herculeana and G. eriense) with multiseriate striae crossed by longitudinal lines and with stigmata. The longitudinal lines are formed by either marginal lamellae or an axial plate, both internal structures...

Gomphonema 15

  1. Valve outline club-shaped (clavate)
  2. Single stigma may be present on one side of the central area
  3. Apical pore field present

Asymmetrical biraphid - Gomphonema valves are symmetrical to the apical axis, and asymmetrical to the transapical axis. In girdle view, frustules are wedge-shaped (cuneate). Striae are not crossed by longitudinal lines, as in Gomphoneis. A stigma may be present or absent on one side of the central area. An apical porefield is present and bisected by the terminal raphe. Many species grow on mucilaginous stalks and can be found in nearly every...

Gomphosphenia 2

  1. Valves cuneate
  2. Axial area broad
  3. Proximal raphe with straight ends

Asymmetrical biraphid - Valves cuneate, with straight or undulate sides. Frustules are never bent or flexed. The raphe is straight and filiform, with straight external terminal fissures (both proximal and distal). Internally, the distal raphe fissure terminates in a helictoglossa. Stigmata are absent. Striae composed of open foramina, which may be obscured externally to give the appearance of ghost striae. Apical porefields, septa and...

Gyrosigma 2

  1. Valve sigmoid
  2. Raphe sigmoid
  3. Striae punctate, punctae form rows perpendicular and parallel to the axes

Symmetrical biraphid - Gyrosigma valves are sigmoid in valve outline. The axial area is narrow and also sigmoid, containing a sigmoid raphe. The striae are comprised of punctate areolae and form rows that are perpendicular and parallel to the apical and transapical axes. The central area is round to elliptical. External proximal raphe ends are deflected in opposite directions from one another. In living cells, two plastids are present....