Brain puffball

Appearance

The fruit bodies of ''Calvatia craniiformis'' grow to dimensions of 6–20 cm tall by 8–20 cm wide, and have a form ranging from pear-shaped, to flattened-spherical, to obovate , to tunicate . At the bottom is a thick, often crumpled base attached to a cord-like rhizomorph, which is often encrusted with surrounding soil. The rhizomorphs are well developed, and when cut into longitudinal section, reveal three distinct tissues: an outer cortex, a subcortical layer, and a central core. The thin and fragile exoperidium is whitish-gray to gray, and initially smooth before becoming areolate . The base extends up one-third to one-half way into the puffball tapering to a point. The gleba is initially whitish, and then yellow-green, and finally brownish-green in older specimens with mature spores.

Spores are spherical, hyaline , and measure 2.5–3.4 μm in diameter. They are thick-walled with a short pedicel , and are ornamented with tiny spines that are roughly equidistant from each other. Capillitial threads are long, hyaline, and branched, measuring 2.4–4 μm thick. They are septate and occasionally have pits on their walls. The exoperidium comprises thick-walled, inflated hyphae mixed with sphaerocysts , while the endoperidium is made of tightly interwoven, thick-walled hyphae. In the rhizomorphs, the hyphae in the central core are several times as thick as those in the surrounding subcortex.

Using light microscopy, the spores of ''Calvatia craniiformis'' are generally indistinguishable from those of ''C. rubroflava'' and ''C. gigantea''; electron microscopy reveals that each has distinctive spore ornamentation. ''C. craniiformis'' features small, well-separated verrucae up to 0.2 μm tall with rounded tips. In comparison, ''C. gigantea'' has larger verrucae that are more irregularly arranged.

Naming

The brain-like surface folds and mature olive-brown gleba are characteristic of ''Calvatia craniiformis'', but younger puffballs that have not yet developed these characteristics may be difficult to identify to species. Another edible puffball, ''C. cyathiformis'' grows to similar dimensions but has gleba that is purple-brown when mature. ''Calvatia fragilis'' is smaller and pink or purple mature gleba. ''C. bicolor'' is a smaller, rounder puffball that could be confused with younger specimens of ''C. craniiformis'', but the former species has more coarsely ornamented spores, and lacks a distinct subgleba. ''Handkea utriformis'' is roughly similar in appearance to ''C. craniiformis'', but unlike the latter it develops a cavernous opening to reveal an olive-brown gleba, and has distinct slits in its capillitial threads.

Distribution

Although ''Calvatia craniiformis'' is generally considered a saprobic species, in controlled laboratory conditions, an ectomycorrhizae between the fungus and American sweetgum was reported in a 1966 publication. A Chinese study showed that ''C. craniifromis'' would readily form mycorrhiza with poplar seedlings on unsterilized, but not on sterilized soil. Later research was unable to establish any similar association between ''C. craniiformis'' and ''Pinus ponderosa''. Brain puffballs grow singly or in groups in fields and open woods, hardwood forests, and wet areas. In Asia, it has been recorded from China, India, Indonesia, Japan, Malaysia, and South Korea. The brain puffball has been recorded from Australia. In North America, its range includes the eastern and southern United States, and Mexico. In Michigan, it is one of the few macrofungi found regularly in black locust plantations. Fruit bodies serve as a food source for several species of flies.

Habitat

Although ''Calvatia craniiformis'' is generally considered a saprobic species, in controlled laboratory conditions, an ectomycorrhizae between the fungus and American sweetgum was reported in a 1966 publication. A Chinese study showed that ''C. craniifromis'' would readily form mycorrhiza with poplar seedlings on unsterilized, but not on sterilized soil. Later research was unable to establish any similar association between ''C. craniiformis'' and ''Pinus ponderosa''. Brain puffballs grow singly or in groups in fields and open woods, hardwood forests, and wet areas. In Asia, it has been recorded from China, India, Indonesia, Japan, Malaysia, and South Korea. The brain puffball has been recorded from Australia. In North America, its range includes the eastern and southern United States, and Mexico. In Michigan, it is one of the few macrofungi found regularly in black locust plantations. Fruit bodies serve as a food source for several species of flies.

Uses

''Calvatia craniiformis'' is an edible species. Young puffballs with a firm, white gleba have a mild odor and pleasant taste. Early 20th-century mycologist Charles McIlvaine noted over a century ago that "the slightest change to yellow makes it bitter." Versatile in cooking, the puffball absorbs flavors well.

In the United States, the Ojibwe used the powdery gleba as a hemostatic agent to staunch the flow of nosebleeds: the spore powder was inhaled through the nostrils. It is now known that this practice can lead to the pulmonary disease lycoperdonosis, which causes symptoms similar to pneumonia. It is also used as a hemostatic agent in Chinese and Japanese folk medicines.