Men, Martians, and Machines, a collection of four stories by Eric Frank Russell first published in 1955. Any of these covers look familiar?
One story was about a machine planet where the machines capture a few of the crew and were ready to dissect them alive in an effort to learn what life was.
"Mechanistria", first published in Astounding Science-Fiction, January 1942, available at the Internet Archive.
"Have you any idea of what they intend to do with us?"
"They'll dissect you."
"Dissect us? Cut us up?"
McNulty scowled and asked, "Why?"
"They dissect all the individualistic. They've been doing it for years, centuries, trying to discover the cause of personal independence. They are intelligent machines, and their intelligence is completely communal." The lobster, or whatever it was, mused and went on, "Upon our own world of Varga there are tiny aquatics of similar type in that they're nothing remarkable as individuals but display high intelligence when functioning in organized groups. They share a racial mind."
They had been taken intelligent crab like creatures from a nearby planet in their solar system and dissecting them for years.
"For many, many circumsolar revolutions they have been trying to conquer the neighbouring water-world of Varga, which is our home planet. Our people have resisted with some success but occasionally some of us are captured, brought here and dissected."
Another short story in the book was about a planet that they landed on where the sunlight was green and the planet was covered by planetary jungle.
"Symbiotica", also the answer to this question; first published in Astounding Science-Fiction, October 1943, available at the Internet Archive.
Sticking my face to the nearest port, I had a look through its thick disc and studied what I could see of the new world. It was green. You'd never have believed any place could be so thoroughly and absolutely green. The sun, which had appeared a primrose colour out in space, now looked an extremely pale green. It poured down a flood of yellow-green light.
The Marathon lay in a glade that cut through a mighty forest. The area immediately around us was lush with green grasses, herbs, shrubs, and bugs. And the forest itself was a near-solid mass of tremendous growths that ranged in colour from a very light silver-green to a dark, glossy green that verged upon black.
The crew quickly learns the trees are carnivorous with very large flat leaves that can swing down and with a very sticky resinous underside trap and lift animals that come too near their trunks.
With a mighty swoosh! the branch immediately above his head drove down. I could almost hear the tree's yelp of triumph as the swipe gave a boost to my imagination.
The spatulate leaf smacked Jepson squarely across his back and a waft of the pineapple-cinnamon smell went all over the place. Just as swiftly the branch swung up to its original position, taking the victim with it. Roaring with fury, Jepson soared with the leaf and struggled furiously while we gathered in a dumbfounded bunch below. We could see that he was stuck to the underside of that leaf and slowly becoming covered in thick, yellowy-green goo as he writhed madly around. That stuff must have been a hundred times stickier than the best bird-lime.
They also find a humanoid life form that lives a symbiotic relationship with certain trees.
"And what have we learned, if anything?" I inquired.
"Well, we know that life on that planet is mostly symbiotic," Jay replied. "Its different forms of life share their existence and their faculties. Men share with trees, each according to his kind. The communal point is that queer chest organ."
The other two stories in the collection are "Jay Score", first published in Astounding Science-Fiction, May 1941, available at the Internet Archive, and "Mesmerica", first published in this collection.