Calvatia cyathiformis f. fragilis
Common Name: purple-spored puffball
Fruiting body 4-6 cm tall, 5-9 cm broad, subglobose, cushion-shaped, to turbinate, tapered abruptly below, the base pleated, pointed, narrowly attached to the substrate; pseudostipe typically lacking; peridium relatively thin, up to 1.5 mm thick; exoperidium at first pallid, glabrous to minutely tomentose, soon buff-brown to liver-brown above, pallid below, with expansion forming thin, appressed light-brown warts over a pallid background, becoming areolate with drying and age, the exposed endoperidum dark-brown, glabrous, covered with scattered light brown warts, these fragmenting at the margins, occasionally peeling away in large sheets, revealing the gleba and eventually a remnant basal cup; gleba at first pale-buff, maturing lilac to purplish-grey, relatively firm and cottony, tending to remain intact; subgleba sub-lacunose, ochre to olive-brown, occupying the lower quarter of the fruiting body, with or without a distinct diaphragm; odor of mushrooms, taste mild.
Spores 4.5-7.0 µm, globose, spinose, with a central droplet; pedicel inconspicuous. Eucapillitium Calvatia type, thin-walled, straight to wavy, brittle, regularly branched, septa common, pits abundant, round, tiny; spores purple-grey in deposit.
Scattered, gregarious, or in fairy rings in native grasslands, pastures, occasionally in open woods; fruiting fall and spring after rains; occasional to locally common in wet years.
Edible when immature and the gleba white, but compare with Scleroderma species (see Comments).
This Calvatia is unusual for its purplish-grey spores a character that distinguishes it from all other members of the genus in California which have olive to brown spores. Though distinctive, it should be compared with Scleroderma species, commonly known as "earthballs," some of which are poisonous. Scleroderma species also have purplish spores which can be spinose but differ in possessing a thick, leathery peridium, and microscopically by the lack of a capillitium. Additionally the genus is mycorrhizal, thus is associated with host trees and shrubs, while puffballs like Calvatia species are believed to be saprobic and are not so restricted. Calvatia cyathiformis f. fragilis is morphologically variable, sometimes possessing a pseudostipe, sometimes not, or intermediate between the two. Because of this, authors have differed in the taxonomic treatment of these "morphs," some considering the non-pseudostipe form a distinct species, Calvatia fragilis while others relegating it to simply a form of Calvatia cyathiformis. In coastal California, specimens mostly lack a pseudostipe but intermediates also occur, thus we have treated this purple-spored Calvatia as a form of Calvatia cyathiformis.