Summary 2

Phormidium is a genus in the taxonomic order Oscillatoriales. All members of this order are characterized by cylindrical cells joined end-to-end to form simple, unbranched filaments. Phormidium is moderately common in freshwater phytoplankton assemblages, but is more likely to be found along shorelines and on damp soil, where it may form dense mats.

About 3

This guide was prepared by Dr. Robin Matthews, former Director of the Institute for Watershed Studies ( and professor emeritus at Western Washington University. In addition to this guide she has also written two ebooks (more on the way) on phytoplankton identification (see the "algae books" link on and an online key to the cyanobacteria (

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  1. (c) rmatth, some rights reserved (CC BY-NC-SA), uploaded by rmatth
  2. (c) rmatth, some rights reserved (CC BY-NC-SA)
  3. Adapted by rmatth from a work by (c) Bryan Milstead, some rights reserved (CC BY-NC-SA)

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