Chorioactis - Description - Microscopic Characteristics

Microscopic Characteristics

Spores are oblong to spindle-shaped, and are flattened on one side; they have dimensions of 54–68 µm by 10–13 µm. The spores each contain 3–5 oil drops. Although the spores have been described as smooth in older literature, when viewed with transmission electron microscopy, they are seen to have minute spots or punctures. The spores develop simultaneously (synchronously) within the ascus, a developmental feature shared with the Sarcoscyphaceae genera Cookeina and Microstoma. Like other members of the Pezizales order, the asci of C. geaster have an operculum—a "lid"—that opens when the spores are discharged. However, the operculum of C. geaster develops a two-layered ring zone upon dehiscence, making it structurally distinct from members of both the Sarcosomataceae and the Sarcoscyphaceae families.

Similar to other Discomycetes, the fruit body consists of three distinct layers of tissue: the hymenium, the hypothecium, and the excipulum. The spore-bearing hymenium, the outermost layer of cells, contains asci interspersed with sterile cells called paraphyses. In C. geaster, the club-shaped asci are 700–800 µm long and 14–17.25 µm thick; they are abruptly constricted at the base to a narrow pedicel. The paraphyses are initially filamentous or thread-like (filiform) but swell with age to resemble a string of beads (monoliform). The swelling of the paraphyses is believed to cause the expansion of the hymenium and subsequent splitting of the fruit body into rays; this development places the asci into an optimal position for spore release and dispersal. Supporting the cells of the hymenium is a thin layer of tightly interwoven hyphae called the hypothecium, and underneath this is a thick layer of loosely interwoven hyphae known as the exipulum. This tissue layer, analogous to parenchyma found in plants, gives the tissue a fibrous texture. The exipulum layer averages 34 µm in diameter, while the hypothecium is 10–14 µm. When viewed with electron microscopy, the dark brown "hairs" on the surface of the fruit body can be seen to be adorned with conical warts or spines.