Sunhede S. 1989. Geastraceae (Basidiomycotina): Morphology, Ecology, and Systematics with Special Emphasis on the North European Species. Synopsis Fungorum, 1. Oslo, Norway: Fungiflora

Geastrum saccatum Fries

Mature fruitbody mostly small to medium-sized. Mycelial layer not encrusted with debris. Exoperidium nonhygroscopic, mostly ± saccate in expanded state. rays mostly 5-8. Endoperidial body sessile. Peristome normally fibrillose and ± well delimited.

Unexpanded fruitbody: Unexpanded, full-grown fruitbodies mostly epigeous (sometimes covered by litter), rarely hypogeous, covered by e.g. a thin layer of sand with mosses, 5-30 mm wide and 6-35 mm high. rounded with an umbo, ± onion-shaped to almost lageniform (figs. 165A,B; 166a-h,j-m,o; 167A:a-f; 172a); sometimes 2 or 3 fruitbodies growing densely together and then ± irregularly shaped (cf. fig. 169B:c). Attached to the ground by a basal mycelial tuft (fig. 167A:c). Surface ± smooth, minutely wrinkled, ± felty, with or without cracks (cf. fig. 166d,h), ochraceous to pale brown. not encrusting litter (even if some dirt sometimes may adhere). No colour changings observed when the surface of the fresh specimens is damaged (cf. Geastrum triplex and Trichaster melanocephalus). Very young immature fruitbodies are shown in fig. 167A:g. Glebal chambers of the young whitish gleba illustrated in fig. 166i.

Expanded fruitbody: Very small to medium-sized species (tab. 2; fig 167B). Colour plate (fig. 236F). Exoperidium splitting from less to more than the middle into 3-12, mostly 5-8 rays of varying shape (figs. 167B; 168; 173C). Specimens with long slender tips of the rays (cf. fig. 173C:a-c) originate from prominently onion-shaped to lageniform. unexpanded fruitbodies. The rays are often ± recurved under the exoperidial disc (figs. 165C-E; 167B:c-e; 168A:h,i) but other positions occur (figs. 165F; 167B:a,b,f,g; 168A:f). The exoperidium is not truly hygroscopic but sometimes dry fruitbodies are found with the rays ± bent towards the endoperidial body (fig. 169B:a,b). Exoperidium mostly ± saccate (figs. 165C-F; 167B:b-g) but specimens with ± planar or arched exoperidial discs are found. The width of the exoperidium varies between 8 and 44 mm (in specimens with horizontally mounted exoperidia 15-97 mm). Pseudoparenchymatous layer when fresh, about 0.5-3 mm thick, at flrst whitish, in age turning to pale ochraceous, hazel-nut brown and in old specimens dark brown, as dry of about the same colours, rarely developing a pseudoparenchymatous collar, not very persistent and often rather soon peeling off (especially if fully exposed to weather and wind) but sometimes remaining ± intact or as remnants in over-wintered fruitbodies. Fibrous layer when totally denuded dirty white, papery as dry and flaccid as wet. Sometimes the mycelial layer of expanding specimens peels off the flbrous layer. Mycelial layer comparatively thick (figs. 166n; 172b), not encrusting debris (see Discussion). ± even to somewhat wrinkled, with or without longitudinal cracks on the rays (cf. figs. 167B:a; 173C); consisting of an outer, ± prominent, rather felty, ochraceous to brownish stratum and an inner, thin to rather thick, loose to ± mealy, beige to whitish stratum; mostly intact in newly expanded specimens (cf. fibrous layer above), in age peeling off but rather often ± intact even in over-wintered specimens.

Endoperidial body mostly sessile (see Discussion), often ± globose, to depressed globose or broadly ovate but sometimes ellipsoid when seen from above (figs. 165C-F; 167B:b-e; 168A; 169A:a-c,f). Diameter 3.5-24 mm, mostly > 5-20 mm (tab. 2; fig. I 68B). Apophysis absent. Stalk mostly lacking or very short (fig. 167C). Endoperidium ± smooth but short protruding tips of hyphae may be seen under a strong lens (see Microscopic characteristics below), mostly rather lightly coloured in beige, brownish grey or greyish brown but darker tints occur. Peristome finely to silky fibrillose. thickened (seen in section), mostly ± well delimited, generally ± conical to mammiform, sometimes almost flat (figs. 165C-F; 167B:b-g; 168A; 169A:ad.f-h, B:b); in unexpanded, onion-shaped to lageniform fruitbodies it may be prolonged into a beak, which rarely may be intact even in expanded specimens (cf. figs. 169A:e); concolourous with, lighter or darker than the surrounding endoperidium, sometimes surrounded by a light-coloured ring (fig. 165D). Columella rather weak to rather tough, columnar, rounded or ± club-shaped (figs. 166j-m,o: 169A:c,f; 172a), in sections whitish to beige. Mature gleba brown.

Microscopy: Basidia with a basal clamp connection or narrowing into a hyphal part ending at a clamp, when young ± bladderlike to ± clavate (fig. 1701,n-q,^), in age either of roughly the same shape, with an apical bulge or gradually narrowing towards a blunt top (cf. fig. 170f,i-k,r). Mature basidia as in fig. 170a-e,g,h, apart from hyphal part, 10-17 x 4.5-10(-12) µm. Hyphal part < 1-6 x 1-2 µm. Pleurobasidia observed (fig. 170m). Sterigmata 3-6, mostly 4-6, I-2 µm long (fig. 170a-i). Subbasidial hyphae ± densely branched, thin-walled, 1-2 µm wide, provided with clamps. Hyphae of tramal plates ± sparsely branched, ± parallel, thin-walled, 1-3 µm wide. Spores in mass brown, as mature, ornamentation included, (4-)4.5-6 µm in diameter, with an oil drop, in TRL yellow brown. SEM-pictures show ± columnar, up to 0.3-0.6 µm high, sometimes ± confluent processes (fig. 17lA-D) and a ± distinct apiculus (fig. 17lB,D). The young spore is symmetrically attached to its sterigma, first broadly obovate, in age becoming ± globose (fig. 170a-e,g,h; Spore wall of fully pigmented spores Cb- and Melz-.

Capillitial hyphae 2-10 µm wide, slightly to very thick-walled (with a narrow lumen), pale greyish brown, light brown to yellow brown in TRL, Cb- and Melz-, with or without surface ornamentation (figs. 171E,F; 172k), which may be Cb±. Fragments of l.5-2 µm wide, thin-walled, clamped hyphae (remnants from the whitish gleba) observed, intermixed. Columella hyphae 1.5-6 µm wide, ± thick-walled, often with a narrow lumen, pale greyish to pale beige in TRL, Cb- to Cb ± (fig. 172i). Remnants of 1.5-3 µm wide, thin-walled, clamped hyphae also observed. Endoperidial hyphae 2-9 µm wide, densely interwoven, thick-walled (often with a narrow lumen; fig. 172h), pale greyish to beige in TRL. Protruding hyphae up to 25 µm wide, thick-walled and inflated (fig. 173A:ae). Peristome hyphae 2-10 µm wide, thick-walled, often with narrow lumen, ± parallel (fig. 172g). Hyphae of the peristomal cover l.5-5 µm wide, thin-walled, branched and clamped (cf. fig. 172c). Pseudoparenchymatous layer consisting of thin-walled, hyphal cells of various shapes and sizes (fig. 172j). Fibrous layer of 2-7 µm wide, ± thick-walled, Cb ± hyphae (fig. 172f). Mycelial layer in the outer brownish to ochraceous part consisting of l.5-6 µm wide, ± thick-walled, sparsely branched, Cb± hyphae (fig. 172d), which are pale greyish beige in TRL. Inner layer paler, consisting of l.5-3 µm wide, thin-walled, branched hyphae provided with clamps (figs. 172e; 173A:f; see Discussion); sparse thick-walled hyphae also observed.