Superman, Swamp Thing, and Solomon Grundy
The recent entry by besamim showing an encounter between Superman and Swamp Thing, which brought up the topic of whether sentient plants count as life, brought to mind another, much earlier encounter between the two. In fact, I think it might have been their first encounter.
I wonder if Rick Veitch had it in his mind when he wrote his issue, because it puts a quite different spin on his story. Also, recall that Grundy is a sort of plant creature in his own right, having a body composed of swamp matter.
Basically, the real Solomon Grundy was in Metropolis some time back, and his body somehow contaminated the sewers. Now there's a chemical reaction going on down there amidst the sewage, and it's generating new Solomon Grundy clones.
One of them climbs to the surface and gets into a tussle with Superman. Meanwhile, another clone is underground with Swamp Thing, who hopes that by examining him, he'll learn something about his own similar nature.
The news sends Swamp Thing's Grundy into a rage, and he heads to the surface with intent to kill. By this point, there are a bunch of Grundys lurking about the sewers.