Water / Oak Trees

Glasses of water come with all sandwiches or desserts but all glasses of water are actually oak trees.
These oak trees are from Michael Craig-Martin’s 1973 piece known as “The Oak Tree.”
A. What I’ve done is change a glass of water into a full-grown oak tree without altering the accidents of the glass of water.
Q. The accidents?
A. Yes. The colour, feel, weight, size …
Q. Do you mean that the glass of water is a symbol of an oak tree?
A. No. It’s not a symbol. I’ve changed the physical substance of the glass of water into that of an oak tree.
[…] Q. But the oak tree only exists in the mind.
A. No. The actual oak tree is physically present but in the form of the glass of water.