On the second day I couldn't resist.
With an eye to the pedestrian traffic I knelt by the mulch and ran my finger under the cap... it was smooth - My first!
A fruiting body of the familiar form, though stout, but without gills - a Bolete.
I know I am not the only one who looks for these little treasures in their daily commute. Like encountering a calm Wildebeest in the T - it's surprising. After a good summer rain I feel like strapping on a pith helmet, snapping back a gin and tonic, and grabbing my rifle to go out and be a brave adventurer in the world of the wild that roars up all around East Cambridge.
Lucky for me all I need is diligent alveolar macrophages and I can leave behind the rifle - it wouldn't do me any good against the invisible storm of spores that will storm up my nares and into my lungs. Better have that gin and tonic though.
Luckier still, I'm no soil-bound microbe. That mulch is a battlefield. The tender hyphae that lie underground just below that silent Bolete are probably pouring out their own armament of digestive enzymes and antimicrobials.
Boletes are mycorrhizal partners of trees. The fruiting body we see is the reproductive structure produced by an expansive subterranean organism that spreads its hairlike hyphae through the soil and around (ecto) and sometimes into (endo) the cells of its partner trees. It's a business deal, there is an exchange of material between the two partners: the fungus is ensured a continuous supply of energy-rich carbon compounds and the tree increases its below ground surface area and thus its access to nutrients like phosphorous, nitrogen, and important trace metals.
Sometimes these mycorrhizal hyphae can connect two trees or plants of different species - allowing transfer of sugars from one tree to another! This is the plant equivalent of siphoning someone's gastank. Some plants have gone so far as to dispense with producing chlorophyll at all! These are called mycotrophs (myco: fungus, troph: nourishment)! There are at least 16 species of mycotrophs in Massachusetts - I'm crossing my fingers for an eventual Dalliance with one of them.
And, as if there weren't enough curiosities to capture my fascination, in my clumsy inspection of this unidentified orange Bolete I accidentally became privy to one of its secrets - exposing its bright yellow inner flesh to air causes it to rapidly turn vivid green and then slowly black! I carried home the young cap that fell off, it became quite dark in the warm palms of my hand, and at home I endeavored to record the color change - the result is in the video below.
These chromatic-shift-inducing oxidation reactions can be localized to different parts of the fruiting body and can be used as a tool in species identification, as can the compounds produced. In the case of our unidentified Bolete it appears, from inspection of the pictures rather than from empirical tests of disturbance, that both the stem and the cap are endowed with the substrates involved. What role do these compounds play in the ecology of our Bolete? The compounds produced by these reactions are not present until the fruiting body has experienced a mechanical disruption of its surface - by the attentions of an amateur myco-fan or the tiny claws of some hard-shelled insect touring about on it. Chemicals produced in this way are likely to be deterrents that dissuade further grazing by insects, but since insect sensitivities vary and not all parts of the fruiting body are reactive there is room for positive interactions that facilitate retention and direction of insects that are effective spore dispersers.
And, lest we run the danger of thinking that it is always the fungus that must arm itself against the culinary designs of others, know that Laccaria bicolor - another mycorrhizal partner fungus - is a career insect killer. "L. bicolor first paralyzes the springtails, quite likely with a toxin... then it extends nutrient-seeking filaments into the insects." But don't think the story ends there! Oh no, this is "Nature, red in tooth and claw" (or is it... in hypha and root hair?) because scientists on the trail of the labeled nitrogen originating from the springtails found it .... in the Eastern White Pine tree.
So, as you read this on your HP Mini, in the park, under the branches of that peaceful pine - remember that you too are tied into this web of sex, death, and survival - keep an eye on those trees.
"Insects & Mushrooms" chapter from Jean Henri-Fabre's book "The Life of the Fly"
The Boston Mycological Club
Mushroom Observer - you can be one too!
More about the Boletales from MushroomExpert.com
Fungus-Insect Relationships by Quentin Wheeler and Meredith Blackwell
Mr. Bloomfield's Orchard
In the Company of Mushrooms: A Biologist's Tale
The day after I first posted this all evidence of these Boletes was completely gone! Was it a gang of school kids or do they suddenly become tasty at some point in development?
In any case, there was suddenly a new patch of them nearby 3 days later. I collected a broken fruiting body to peak under it's cap - it's bright red (don't know if it is this color while still attached - I guess I need to add a little pocket mirror to my walking gear if I can't commit to snapping little mushroom caps). Slicing through it you can easily the thick meaty cap and thin layer of tubes that form the pores.
I can't narrow this down to species with confidence but if I had to pick one right now I'd go with: Boletus subvelutipes. If you see the definitive characteristics that can rule this out or in then please enlighten me with a comment - Thank you!