OBSERVATIONS ON THE EUGLENOID COLACIUM WITH SPECIAL REFERENCE TO THE FORMATION AND MORPHOLOGY OF ATTACHMENT MATERIAL1

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Abstract
SUMMARY: Certain taxonomic features of Colacium Ehrb. are evaluated from field, clone, and literature studies. A main character, morphology of the attachment material, is shown to be partially nutritionally controlled: stalks and cushion holdfasts are produced in soil‐water but rarely in plain Euglena medium; ferric and manganouns compounds influence the, formation of stalks in C. vesiculosum; single clones of C. vesiculosum produce holdfast characteristics of C. arbuscula, C. steinii, C. sideropus, and C. simplex when grown in soil‐water medium. Stalk formation is rare in C. vesiculosum but common in C. mucronatum and Colacium sp. (from the rectum of damselflies). Some questionable negative observations, incompleteness of certain species descriptions, and overlapping of species characteristics lead us to believe that C. sequabile, C. stentorinum, C. calvum, C. multoculata, C. elongatum, C. ovale, C. arcuatum, C. cyclopicola, and C. pyrenophorum = C. vesiculosum. Our C. vesiculosum attached to Mougeotia and Volvox tertius, suggesting that the epiphytic species of Colacium, C. epiphyticum, and C. parasiticum need to be studied in clonal culture to determine if they have substrate specificity, and if they represent valid species. Recommendations are made for identifying and naming species.

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