He picked up a chunk of shale, and lobbed it into the tree. The reaction was violent and immediate. The formerly quiescent limbs whipped sinuously through the air, their thorny armament glinting in the light. Madsen felt the back of his neck tingle at the hiss of their passage. Dozens of black, hornet-like insects took wing, and buzzed angrily and aimlessly around until the agitated motion subsided and the tree sank slowly into its former somnolence. "How does it work?" asked Madsen. "The thorns, they're almost instantly lethal. Notice those wasps, or whatever they are?" "Yeah." "Well, they live in those trees, and pollinate them. They lay eggs in the game that the tree polishes off. When the larvae graduate and get their wings, they make a brief nuptial flight, and set up housekeeping in a similar tree. Other insects stay away. It's a beautiful case of highly specialized symbiosis." "Funny, eh?" "Not very. You might say our position is similar, to a degree. How are you feeling now?" "A lot better, except for the ache. Your throat seems to be coming along all right, too." His eyes ranged the slope, estimating the distance to their initial resting place. "Man alive, I was lucky to be in range!" "You were at that, Madsen. There's just one chronic bug in energy weapons, the old law of inverse squares. Short range tools, that's all." "You said it. Say, Morley--" "Yes?" "Doesn't a symbiotic relationship usually refer to some type of parasitism? Sort of a put and take game, with one organism doing all the putting, and the other, all the taking?" Can it be? thought Morley, incredulously. Honest gratitude was natural, but the idea that Madsen's granite exterior might conceal a slowly burgeoning respect--! "Not exactly," he said carefully. "Often there is a mutual dependence, as with us. That's what I meant to say in the first place." "Thanks. I feel, well, pretty foolish about being so careless, and holding us up. Not that I'd have gone on walking into that tree, mind you. And I'd hate to have you think of me as a human--liana, or remora, or something." "Don't be silly. We're partners, aren't we?" "Yeah, that's true. Morley, I--" "Well?" "Thanks, a lot." "Er--that's all right. Skip it." * * * * *