Morganella pyriformis is a puffball. The mature fruiting body of the fungus bursts open and releases the spores, after some physical force has been applied. I've been known to help a few of these along.
Prior to 2003, this fungus was known as Lycoperdon pyriforme. It has since been moved out of the genus Lycoperdon based on molecular evidence and morphological difference to other members of the genus. No longer is the evocative common name suggested by Tom Volk a literal translation of the genus name. A different common name, pear-shaped puffball, is perhaps more proper. After all, the epithet pyriformis does mean “in the form of Pyrus (pear)”. However, I'll personally use the one proposed by Tom, because I know I'll never forget it.
Tom's article also has a story about the results of deeply inhaling the spores of puffballs (don't do it). Illustrations and descriptions of Morganella pyriformis are available from both Mykoweb and Michael Kuo's MushroomExpert.com.
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Thanks for posting the photo, Daniel. Your site is a valuable asset for keeping me updated on the taxonomic state of so many different plants and fungi. To address today's photo...yep, Tom's name is much more fun. There's something about fungi that seems to elicit more visceral reactions in us...even "sober" scientists can't resist epithets like "lycoperdon" and, one of the most unabashedly brazen, the scientific name for the common stinkhorn. (You can find that at Michael's website...just search the site index for "stinkhorns."
Matt
Without following your link to Tom Volk's website, I would never have known that Lycopersicon was the "wolf's peach"! Thanks for sharing the URL.