Hypomyces cervinigenus

H. cervinigenus has perithecia that are white to pale buff with a waxy texture. The ascospores are two-celled, smooth-walled, and measure less than 25 μm long.^[1] The anamorph form of the fungus is known as Mycogone cervina.^[3]

The fungus initially forms a white, loose, cottony subiculum (a mat-like structure of fungal threads) that becomes more compact as the reproductive structures develop. These threads (hyphae) are branched, transparent (hyaline), divided by walls (septate), and uniformly less than 3 micrometres (μm) in diameter.

The reproductive structures, called perithecia, appear as the fungus matures. These structures are either separate or densely compacted in patches up to 1 square centimetre. When fresh, the perithecia are white and translucent, but as they age and dry, they become waxy in appearance and light yellow, buff, or amber coloured. They are roughly globose (spherical) to ovate (egg-shaped) or papillate (with a nipple-like projection), measuring about 165–350 μm high by 132–265 μm wide.

The wall of each perithecium is 10–12 μm thick with a complex cellular structure. The papilla (tip) of the perithecium has a distinctive ostiole (opening) lined with filamentous structures called periphyses that are 15–20 by 2 μm in size.

Inside the perithecia are the asci, elongated sac-like structures containing the spores. These asci are long and linear, measuring about 100-–142 by 2–4.5 μm. They have thin walls except at the apex (tip), where there is a thickened cap 1–2 μm thick with a distinct pore through which spores are released. The ascospores themselves are arranged obliquely in a single row within each ascus. They are hyaline (transparent), fusiform (spindle-shaped) to cylindrical, and usually 2-celled, measuring about 15–26 by 1.5–5 μm. The spores typically have acute (pointed) ends but can sometimes have a more obtuse (blunted) lower end. The cell wall is smooth, and the cytoplasm inside often appears vacuolated, with a septum (dividing wall) in the middle that may sometimes be difficult to see.

H. cervinigenus can be found growing on elfin saddle (Helvella) mushrooms in Europe and North America.