The integral trees

For a long, long time the State used slower-than-light spacecraft to prepare star systems for colonization by Man. Normally the ramseeders traveled centuries-long circuits which began and ended at Earth. Normally the mixed crew of citizens and "corpsicle" convicts remained with their ship. Normally ultimate control of the mission was exercised by a built-in cyborg "adviser", the true despot of the tiny State microcosm that was the ship. But little happened normally when Discipline reached the double-star system of T3 and LeVoy's Star. There an immense doughnut-shaped gaseous envelope had formed around a neutron star--and a vast volume of that nearly empty cloud was comfortably habitable to Man. Though it had very little usable land, the Smoke Ring had evolved a huge variety of free-fall life-forms, most of which were edible and all of which could fly.