The free gills are white, as is the spore print. The oval spores measure 9–13 by 6.5–9 μm; they do not turn blue with the application of iodine. The stipe is white, high by wide, and has the slightly brittle, fibrous texture typical of many large mushrooms. At the base is a bulb that bears universal veil remnants in the form of two to four distinct rings or ruffs. Between the basal universal veil remnants and gills are remnants of the partial veil (which covers the gills during development) in the form of a white ring. It can be quite wide and flaccid with age. There is generally no associated smell other than a mild earthiness. thumb|Image of Amanita muscaria by Theodore Green (1933) Although very distinctive in appearance, the fly agaric has been mistaken for other yellow to red mushroom species in the Americas, such as Armillaria cf. mellea and the edible A. basii—a Mexican species similar to A. caesarea of Europe. Poison control centres in the U.S. and Canada have become aware that (Spanish for 'yellow') is a common name for the A. caesarea-like species in Mexico. A. caesarea is distinguished by its entirely orange to red cap, which lacks the numerous white warty spots of the fly agaric (though these sometimes wash away during heavy rain). Furthermore, the stem, gills and ring of A. caesarea are bright yellow, not white. The volva is a distinct white bag, not broken into scales. In Australia, the introduced fly agaric may be confused with the native vermilion grisette (Amanita xanthocephala), which grows in association with eucalypts. The latter species generally lacks the white warts of A. muscaria and bears no ring. Additionally, immature button forms resemble puffballs.
The free gills are white, as is the spore print. The oval spores measure 9–13 by 6.5–9 μm; they do not turn blue with the application of iodine. The stipe is white, high by wide, and has the slightly brittle, fibrous texture typical of many large mushrooms. At the base is a bulb that bears universal veil remnants in the form of two to four distinct rings or ruffs. Between the basal universal veil remnants and gills are remnants of the partial veil (which covers the gills during development) in the form of a white ring. It can be quite wide and flaccid with age. There is generally no associated smell other than a mild earthiness. thumb|Image of Amanita muscaria by Theodore Green (1933) Although very distinctive in appearance, the fly agaric has been mistaken for other yellow to red mushroom species in the Americas, such as Armillaria cf. mellea and the edible A basii—a Mexican species similar to A. caesarea of Europe. Poison control centres in the U.S. and Canada have become aware that (Spanish for 'yellow') is a common name for the A. caesarea-like species in Mexico. A. caesarea is distinguished by its entirely orange to red cap, which lacks the numerous white warty spots of the fly agaric (though these sometimes wash away during heavy rain). Furthermore, the stem, gills and ring of A. caesarea are bright yellow, not white. The volva is a distinct white bag, not broken into scales. In Australia, the introduced fly agaric may be confused with the native vermilion grisette (Amanita xanthocephala), which grows in association with eucalypts. The latter species generally lacks the white warts of A. muscaria and bears no ring. Additionally, immature button forms resemble puffballs.