ALL0-9ABCDEFGHIJKLMNOPQRSTUVWXYZ Share This Tweet Share A single-celled, microscopic organism having a cell wall but no chlorophyllReproduces by cell division. Related Images:Related Articles: Glossary: ActinomyceteGlossary: Bacillus thuringiensisGlossary: Crown gallDisease and DisordersFungus Gnats – Pest