From Seeds of the Dusk by Raymond Z. Gallun

Astounding Science Fiction, June 1938

In the distant future, in the remote desert, a highly evolved corvid confronts an unusual visitor. An invader from Mars. Unnerved, the plucky post-raven hunter-gatherer imagines the worst. But really, how dangerous could an intelligent and civilized plant be?

It was a bulging, slightly flattened sphere, perhaps a yard across. From it projected flat, oval things of a gray-green color, like the leaves of a cactus. And from these, in turn, grew club-like protuberances of a hard, horny texture--spore-pods. One of them was blasted open, doubtless by the pressure of gas accumulated within it...

The entire plant bristled with sharp spines, and was furred with slender hairs, gleaming like little silver wires...

Kaw was no botanist, certainly; still he could recognize the object as a plant of some kind. But those little, bright, eye-lenses suggested an unimaginable scrutiny...

He hopped forward cautiously toward the invader...lightly and swiftly his beak shot forward. It touched the tip of a sharp spine.The result left Kaw dazed. It was as though he had received a stunning blow on the head...

Electricity...Electricity generated chemically in the form of the invader, by a process analogous to that by which, in dim antiquity, it had been generated in the bodies of electric eels and other similar creatures.

However, there was a broad difference here between the subject and the analogy. Electric eels had never understood the nature of their power...The spore plant, on the other hand, comprehended minutely. Its electric organs had been minutely preplanned and conceived before one living cell had been caused to grow on another. And these organs were not inherited but were designed...

Instead of taking the easy way out, and envisioning motile sapient plants(Morticia's beloved African Strangler comes to mind), Gallun tried to work out how a real plant intelligence might evolve. They say he was known as an idea man. Obviously, fire and metallurgy would be problematic for them.

Being plants, I suppose the notion of growing what they needed struck him as more reasonable.

It is not to be supposed that it must always lack, by its very nature, an understanding of physics and chemistry and biological science. It possessed no test tubes or delicate instruments, as such things were understood by men. But it was gifted with something--call it an introspective sense--which enabled it to study in minute detail every single chemical and physical process that went on within its own substance.

It could feel not only the juices coursing sluggishly through its tissues, but it could feel, too, in a kind of atomic pattern, the change of water and carbon dioxide into starch and free oxygen. Gift a man with the same power...that of feeling vividly even the division of cells, and the nature of the protoplasm in his own tissues--and it is not hard to believe that he would soon delve out even the ultimate secret of life. And in the secret of life there must be involved almost every conceivable phase of practical science.

Meanwhile, back on the dying Earth, the invasion proceeds apace...

Now Kaw had but one thought, and that was to get away. Still dazed and groggy, he leaped into the air. From behind him, in his hurried departure, he heard a dull plop.

More billions of spores, mixing with the wind, to be borne far and wide.