The Liberty Hyde Bailey Conservatory has more than plants: Flower pot parasol aka plantpot dapperling:
Details from my friend Kathie Hodge:
Flower pot parasol (US)
Plantpot dapperling (UK)
Family: Fungi: Agaricaceae
Native to: Neotropics
This handsome yellow mushroom pops up frequently in greenhouses and potted plants. Its saprobic mycelium lives in the soil, digesting organic matter. The actions of its enzymes help break down soil and mulch, making mineral nutrients more accessible to plant roots. Thus it does not harm nearby plants, and in our opinion it sometimes outshines them. The yellow mushrooms pop up when conditions are right. They produce spores that help the fungus spread. These mushrooms are not dangerous to touch or smell, but cause stomach upset if eaten.
Horticultural notes: This mushroom is believed to be native to the tropics. It is probably introduced to greenhouses in potting soil.