Donald Moffitt - Genesis 01

true leaves, with the help of a little biological engineering by the Nar, learned to conserve water rather than respire it.
    And like all plants, it reached out for water in the only way it could.
    The leaves were dark on one side, silvery and reflective on the other. With the cunning phototropism of plant life, the leaf system used available starlight to change the tree’s direction of spin. Instead of rotating end over end, the tree began, over a period of years, to twirl on its axis. That encouraged the branches and roots to grow out laterally—to spread its sails and enable the tree to move by the pressure of starlight. At the same time, the axial rotation put a stop to the tendency of the trunk to grow taller and instead made it grow thicker—better able to support the opening umbrellas.
    Now the tree was a true spacefarer—able to follow the tenuous currents of life-giving vapor wherever they led, engulfing new cometary cores and sucking them dry, building its own tissues in the process.
    The cometary halos of neighboring stars are contiguous. The vacuum-poplars were seeding themselves outward. Already, thinly spread forests of them grew around Juxt One, with little help from the Nar, and they had been found in the cometary shells of stars as distant as twenty light-years.
    When the Nar needed a new starship, all they had to do was tag a likely specimen, tow it to planetary orbit, and outfit it with living quarters, a parasitic ecology, and simple biological controls to make it deploy its foliage as commanded.
    Man, for all his technical superiority, had never brought his own space-grown trees to their full potential. With his shorter life span, man had to hustle between the stars. The Nar could afford a leisurely sail, pushed by the gentle pressure of starlight.
    “I … I’ve seen pictures of trees,” Kerthin breathed in wonder, “but I never expected …”
    “It’s hard to grasp,” Bram agreed. “Lowstation looked pretty big to me. But it would just be a speck next to that thing. You wouldn’t notice it at all. You could hide it inside a twig at the end of the branches.”
    As they watched, the moon-sized disk underwent a startling change. It was growing darker on one side. A wave of dark green rippled across its face until, within a few moments, it was neatly bisected by a geometrically straight line—silver on one side, green on the other.
    “We’ve all been very fortunate to see that,” the Nar attendant said. “Our timing is lucky. We’ve just seen the tree decide to make a small attitude correction.”
    “What happened?” Kerthin said.
    “The leaves,” Bram said. “It turned its leaves over on half the reflecting surface. Over the next few days, it’ll get a small push that’ll—” He checked the cloud-marbled surface of the Father World below. “—line up the trunk vertical to its orbit. I guess it doesn’t like tidal forces.”
    “You are correct,” the Nar attendant said. “The star trees are uncomfortable in the vicinity of large planetary gravitational fields and try to avoid them unless they are forcibly guided.”
    Bram turned mildly pink. He hadn’t meant to be overheard.
    “How do they do that?” somebody asked from the other side of the cabin.
    “We can deceive the tree with various synthetic hormones,” the attendant said. “There’s a pumping station in the trunk. There are also simpler means. We can throw bait—release water vapor ahead of it. Or use artificial light.”
    “Poor tree.” Someone laughed. “The carrot leading the stick.”
    “I’ll have to learn that trick,” Nen said, twisting around in her seat to face Bram and Kerthin. “About the hormones, I mean.”
    “Don’t pay any attention to her,” Trist said. “She’s been doing it for years. She’s got all the hormones she needs.”
    “Where the hormones—” Nen started.
    “There moan I,” Trist finished for her. “How about you, Bram?”
    The line had been shamelessly stolen from some ancient author; Trist had used it years ago in the bachelor lodge during his ribald period. Bram smiled helplessly at Kerthin, apologizing for Trist, but Kerthin wasn’t smiling. Bram tried to think of something lighthearted to say before the mood got too chilly.
    “We’re about to turn over for our final approach now,” the Nar attendant said. He must have received a signal from the pilot through his glove.
    A murmur of disappointment rose from the passengers. Trist raised an eyebrow