• Category
  • Length Range
    96-156 µm
  • Width Range
    21-24 µm
  • Striae in 10 µm
  • Synonyms
    Navicula legumen f. major A.W.F.Schmidt 1876
  • Reported As
    Pinnularia legumen (Krammer and Lange Bertalot 1986, pg. 413, Pl. 184, Fig 1)



Valves are linear and triundulate. The central undulation may be so subtle that the valves appear biundulate. Apices are rostrate to subcapitate, about half of the width of the distal undulations. The axial area is linear-lanceolate, about one third of the valve width. The central area is large and round. Small round depressions are found on the external valve surface in axial and central areas. The striae are radiate at center valve, becoming convergent at the apices. The raphe is lateral and almost straight, with very slightly expanded proximal ends and terminal fissures that appear as bayonet-shaped or semi-circular in light microscope images.


Pinnularia undula var. major occurs in the benthos of lakes of northeastern US.

Original Description

  • Basionym
    Pinnularia legumen f. major
  • Author
    A.W.F.Schmidt 1875

Original Images

Pinn Undula Major Orig Ill real
Pinn Undula Major Orig Descr

Cite This Page

Friedman, N., Potapova, M. (2021). Pinnularia undula var. major. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/pinnularia-undula-var-major


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Pinnularia undula var. major from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.