Though the image of these things isn't very clear, it looks like one of the many species of artillery (or bird's nest) fungi. The fruiting bodies (the part you see above ground....mushrooms) are attached to the 'working' part of the fungal organism, the hyphae and mycelium. They would resemble roots.

I suspect that you gave your plant a vacation outside last year and that the organic based potting medium was inoculated with the spores. These fungi (if that's what you have) are decomposers and not at all harmful to your plant, but I sure wouldn't want one of those species inside my home. The spores (what looks like seeds) are expelled far distances and stick to any and everything. Keep them removed and disposed of as soon as you see them.

As I recall from a few years back, someone here in the gardenweb complained of mysterious black spots (that wouldn't wash off) on his living room wall and windows. One of these sneaky little mushrooms was to blame, lol.

Here is a link that might be useful: {{gwi:1193740}}

rhizo - thanks for the response. the picture that you provided doesn't look exactly the same, but i know that you mentioned that there are many species of this type.

the thing that i wonder about with this is that my zz has never been outside - even in the summertime he lives in our living room. i did, however, re-pot him earlier this year. do you think that there is a possibility that the potting soil that i purchased could have had the spores in it? i think i'll be upset if my local greenhouse is selling spore-laden soil!

is removing them by hand and disposing of them enough to get rid of them, or will i need to use some sort of fungicide?

thanks again for your help - i'm very glad to hear that these won't kill my zz! :)

As long as what you have looks something like the image I attached, I'm thinking you have one of those artillery fungi. Yes, there are scads of them, and each different from the other.

Fungicides are not called for. Removal of those temporary fruiting bodies manually is about all you can do. Remember though, the permanent and 'working' part of your mushrooms are probably all throughout your potting soil by now (nearly invisible thread-like mycelium and hyphae). If what you've observed is one of these interesting fungi, the mushrooms (fruiting bodies) will continue to pop up from time to time.

The potting medium had to have been inoculated somewhere along the line. Where is anyone's guess. It's pretty difficult to maintain total sterility of the product from the time it's produced.

my zz plant recently grew what looks like a pine cone. i cant image it being a pest but is it normal? should i leave it or pull it off? can i plant it? i havent been able to find anything about cones growing on zz plants. any help? thanks.