Collection location: Santa Rosa, Sonoma Co., California, USA [Click for map]
In October I noticed a large mass of these in some mulch, after it rained, while walking in my neighborhood. It stopped raining and the mulch was in a sunny location so I brought some home to see if I could raise them and find out what they were. As it happens, those left behind did manage to mature, in a less luxurious manner, than the adoptees. I photographed them every morning about the same time. I’ve left off a couple that didn’t show much change.
Sorry, I forgot to come back to these after Darvin commented. I didn’t get any photos of those left behind. What I remember is they retained the cylindrical shape and had a round opening, at the top, that was slightly smaller than the diameter of the cylinder. And I don’t remember, now, what made me decide they were Nidula candida. I thought it would be a fun and informative science project, but next time I’ll leave them where they are and photograph them in situ.
Looking at pictures of Cyathus olla I’m inclined to agree that that’s more likely.