• Webster's Revised Unabridged Dictionary
    • n Protococcus (Bot) A genus of minute unicellular algæ including the red snow plant (Protococcus nivalis).
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Century Dictionary and Cyclopedia
    • n protococcus A genus of algæ, typical of the order Protococcaceæ and class Protococcoideæ. They are in the strictest sense unicellular plants, being spherical, unbranched, and single, or gathered into irregular groups or clusters. They are primarily always filled with chlorophyl-green cytioplasm, which often changes to red by exposure or other circumstances. They multiply rapidly by repeated bipartition of the cell-contents. P. viridis is exceedingly abundant everywhere, forming broadly expanded strata of yellowish- or darker-green color on trunks of trees, moist rocks, walls, timbers of shaded buildings, old fences, etc. P. nivalis is the well-known “red snow” which frequently covers large tracts of snow in arctic or alpine regions in a very short time.
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Chambers's Twentieth Century Dictionary
    • n Protococcus prō-tō-kok′us a microscopic vegetable organism forming the green scum upon trees, tiles, &c.
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Webster's Revised Unabridged Dictionary
NL. See Proto-, and Coccus
Chambers's Twentieth Century Dictionary
Gr. prōtos, first, kokkos, a berry.


In literature:

You beg the question, I think, in saying that Protococcus would be doomed to eternal similarity.
"More Letters of Charles Darwin" by Charles Darwin
On several patches of the snow I found the Protococcus nivalis, or red snow, so well known from the accounts of Arctic navigators.
"A Naturalist's Voyage Round the World" by Charles Darwin
Mine host with whom I lodged had a microscopical mount of the Protococcus nivalis in excellent state of preservation.
"Scientific American Supplement, No. 385, May 19, 1883" by Various
Where the ordinary plants cease to exist the snowy protococcus holds undisputed sway on the extensive snow fields.
"The Mountain that was 'God'" by John H. Williams
"A System of Practical Medicine by American Authors, Vol. I" by Various