Many hyphal segments are transformed into giant, atypical cells. All cell organelles are hypertrophic. When infection occurs before organogenesis, no organs such as pileus, stipe, lamellae can develop. The resulting large, irregular, fungal lump may only be designated as a tumorous growth. Focal cell wall thickening may be a defence mechanism of the host.
Mitochondria proliferate and form long chains and rings.
Experiments were also repeated with a diluted spore suspension containing less than 100 aleuriospores in one drop. Such a tiny drop of spore suspension on the pileipellis of A. bisporus , cap size of 20 mm, is shown. One drop of aleuriospores readily induces tumoral hyperplasia on the pilei of the host primordia. Experimentally, even less than 10 aleuriospores were able to induce such solitary nodules. 2- Parasitic hyphae grow and sporulate mainly in superficial lesions.