with more or less distinctness
Plate VII, B.
Photomicrograph of double twisted ribbon-like form of Spirophyllum Ferrugineum from city water, Madison, Wis., x640.
The dark masses are gelatinous ferric hydroxide. Unstained.
(cropped from border and page)
illustrating Edmund Cecil Harder. Iron-Depositing Bacteria and their Geologic Relations. USGS Professional Paper 113. (1919) *
Stanford copy, no date of digitization
More often, however, the two filaments forming such a thread can be traced with more or less distinctness.
21 February 2014
tags: E. C. Harder; drawing; iron-bacteria; water