On this Ming Dynasty scroll from the Metropolitan Museum you can easily see the lingzhi, growing right out of the earth. Given its close resemblance to a flower, and at times a rock, you really have to look closely to know what you are seeing. Above the lingzhi is growing near clumps of flowers, as we often see on mahjong tiles.
From C.A. S. Williams Chinese Symbolism and Art Motifs
"The lingzhi, or Plant of Immortality, is a species of fungus, probably the Polyporus lusidus, which grows at the roots of trees."
The above two sets of flowers might resemble lingzhi, but these are felt to be rocks.
The Flowers below are lingzhi; you will see the difference:
The above ones are lingzhi, and you can see that the fungus is much more rounded, with a noticeable stem on these tiles at least.
Here is a photograph of a real lingzhi, taken from Wikipedia:
This one has the more rounded head than the ones we saw on the Mahjong tiles above.