A E van Vogt's "The Harmonizer" (short story, plant sf, free): Beware! A super-peacekeeper polices the earth!
I think the best part of this story is van Vogt's unique style. When he's in his element, he can enliven up even the craziest ideas!
Story summary.Especially engineered, immortal, peace-keeping, "ibis" plants arrived on earth 80 million years ago, accidentally, via an alien ship crash. These plants cannot stand "brutality" in their environment, & are equipped to deal with it.
Their shipment was not meant for earth. A later alien expedition culled them on earth - all except one which was rather well hidden. By then, these peacekeeper plants had already taken care of the violence among the dinosaurs.
Now that humans are fighting a major war, will the surviving peace keeper get into action?
Fact sheet.First published: Astounding, November 1944.
Download full text as parts of the scans of Astounding issue where it originally appeared.
Listed among the stories from John Campbell's Astounding/Analog.
Related: Stories of A E van Vogt.