Cowboy's Handkerchief

The cap of H. eburneus is 2 to 7 cm (0.8 to 2.8 in) broad, with a shape ranging from convex to flattened, sometimes with an umbo (a raised area in the center of the cap). In age the cap margin sometimes becomes elevated and the center of the cap depressed. The cap is pure white, and depending on the moisture in the environment, may be glutinous to sticky. The cap surface is smooth, the margin is even and in young specimens, rolled inward and covered with short fibrils. The flesh is soft and white, thick in the center of the cap but thinning toward the margin. The odor and taste are mild. The gills are somewhat arcuate-decurrent, meaning they are shaped like a bow, curving upward and then running down the stem for a short distance. In terms of spacing, they are subdistant to distant, so that space can be seen between them. The gills are moderately broad, broadest near the stem, narrowed in front, pure white, slightly yellowish or buff with age or when dried. The stem is 4 to 15 cm (1.6 to 5.9 in) long, 0.2 to 1.5 cm (0.08 to 0.6 in) thick, equal in width throughout its length to somewhat tapered downward or with a greatly attenuated base, and glutinous. Its surface is silky beneath the gluten. The top of the stem is covered with short fibrils, pure white, sometimes becoming grayish or dirty with age. It is initially stuffed with cotton-like mycelia, then later becomes hollow. …

The fruit bodies of H. eburneus grow on the soil, mostly in coniferous woods, thickets and grassy areas. The fungus prefers soil that is moist, mesic, loamy and calcareous. The fungus is widely distributed in North America. It is also found in Europe (Poland and Portugal), Israel and North Africa.

The mushroom is edible, although it may not be appealing to many due to its sliminess. In China, a yak milk beverage is made with H. eburneus and yak milk, by lactic acid fermentation with Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus acidophilus as mixed starter.

Bioactive compounds. Several fatty acids with bactericidal and fungicidal activity have been isolated and identified from the fruit bodies of H. eburneus. The bioactive fatty acids are built upon a chemical structure called γ-oxocrotonate. The following gamma-oxocrotonate derivatives have been identified from the mushroom: (2E,9E)-4-oxooctadeca-2,9,17-trienoic acid, (2E,11Z)-4-oxooctadeca-2,11,17-trienoic acid, (E)-4-oxohexadeca-2,15-dienoic acid, (E)-4-oxooctadeca-2,17-dienoic acid, (2E,9E)-4-oxooctadeca-2,9-dienoic acid, (2E,11Z)-4-oxooctadeca-2,11-dienoic acid, (E)-4-oxohexadec-2-enoic acid, and (E)-4-oxooctadec-2-enoic acid. The compound (E)-4-oxohexadec-2-enoic acid has been investigated for potential use as a fungicide against the oomycete species Phytophthora infestans, a causal agent of potato and tomato late blight disease. Additional secondary metabolites discovered in H. eburneus include the ceramide compound named hygrophamide ((2S,3R,4R,2'R)-2-(2'-hydroxy-9'Z-ene-tetracosanoylamino)-octadecane-1,3,4-triol), and the β-carboline alkaloids known as harmane and norharmane. …