First, I have to point out that Stemonitis splendens (Stemonitis sp.) typically does not appear as in my photos. When it runs out of food, or conditions become otherwise unfavorable, it sprouts super-thin black hairs on which brown spore groups grow. The spores eventually fall off and are spread by wind, and possibly other means. I don't know what this slime mold looks like in its normal thriving state. Perhaps it's not very noticeable when it's normal. It only grows sporangia when it must.
So, Stemonitis sp. is a type of slime mold. There are different forms of slime molds, but this one is particularly disturbing (to me) because it's basically "The Blob" until it becomes hairy, as in my photos.
I saw the Steve McQueen version of "The Blob" when I was a little kid. The memory of "The Blob" gave me frights as a child when I'd notice shadows under doors and caused me nightmares for many years. The most recent nightmare was just a few years ago... The dream was one of those commonly experienced 'chase' situations that most people have from time to time, in which someone or some 'thing' is after you. Also, "The Blob" ruined my desire to enjoy puddings and gelatins. I'm over that food problem now and will eat such things, but, if I have a choice between pudding/gelatin and anything else, Else always wins.
So, slime molds (slime/s), like Stemonitis sp., are large single-celled organisms containing multiple nuclei and lacking cell walls. Such organisms are called 'plasmodia' and are made up of protoplasm, the same stuff inside most single cells. They move by pulsating, though I have no idea how they manage to pulse in the first place.
Stemonitis sp. are different from other molds and fungi in that they do not grow roots into surfaces. Rooting would hinder their ability to move about in search of food. They creep along, blob-like, enveloping bits and pieces of organic matter and 'consuming' those bits. Unlike "The Blob" they do not subsist on living matter, but may pass over living plants in their search for other organic debris foodstuffs.
Stemonitis sp. are not edible by humans. Even if they were, they would barely make a decent snack. However, they do provide food for slugs and other creepy crawlies, which will eat just about any debris they find. I often find slugs feasting on the poo residue on scoops we use outside to clean up the yard when our dog has to go #2.
For the sake of posterity, my first impressions upon seeing the mass of sporing slime were as follows:
I thought that someone had stuck a patch of stringy brown fuzz to the window frame. Why would someone do this? I don't know, but I've seen far more random things than a patch stringy brown fuzz on a windowpane.
I should mention that, in this sporing state, the slime is not readily visible, perhaps having dried out. I suspect the slime was thriving in our remarkably rainy Spring. Then, the recent day and a half of no rain, plus a wee bit of sunshine, may have dried out the slime enough to cause this batch to go into spore mode.
The black stems, at first glance, resembled a patch of black velcro to which the stringy brown fuzz was attached. As I leaned in for a closer look I noticed the dusty brown stuff laying on the windowsill beneath and to the side of the fuzz and recognized it as spore dust. Even after discovering that this was a patch of mold I thought it looked like something else. The storefront where this was found had once been home to a dealer of saltwater aquariums, fish, corals, etc. and I considered the sporangia to resemble a sea anemone.
Spring is a good time for finding many odd things. Later, in the evening of the same day, I found a large Cleopatra moth at a local convenience store. I have photos of it to post as well.
I hope this information will be of use to someone else in the future.
Thanks to http://www.messiah.edu/Oakes/fungi_on_wood/club%20and%20coral/species%20pages/Stemonitis.htm for the scientific details concerning my strange find.