cryoflora, algae that live in snow and ice. The well-known and widely distributed red snow (q.v.) is caused by Chlamydomonas nivalis and diatoms; brown snow by desmids, diatoms, and blue-green algae; green snow by Euglena or Chlamydomonas; and “black” snow by Scotiella nivalis and Raphidonema.