Hemiamyloidity in mycology refers to a special case of cell wall amyloidity where the blue staining by iodine only occurs when the tissue was pretreated with potassium hydroxide solution (KOH) or other strong bases, whereas direct application of iodine causes a red reaction when using Lugol's solution, but no reaction when using Melzer's reagent. Hemiamyloidity is so far only known in Ascomycota, but here widespread and an important taxonomic distinction criterion. If cell walls stain blue by iodine reagents without pretreatment with KOH, this is called euamyloid. The term amyloid comprises both variants.