Hothouse

by Brian Aldiss

Lily-yo, leader of a small, matriarchal human tribe, decides that the group should break up, as the adults are too old, and should go to the "Tips", the dangerous top levels of the forest, to go "Up". "Burnurns" – transparent seed-casings – are collected, and the adults seal themselves inside after which the young attach them to the webs of the giant spider-like plants called "Traversers", which travel into space to receive more intense sunlight and escape the parasitic tigerflies; as planned a traverser brushes against the sticky pods and carries them to the moon (which now has a breatheable atmosphere).

The unconscious adults reach their destination, where they discover they have transformed into "Flymen", mutated by space radiation into flight-capable forms. They meet others and are impressed into an expedition back to Earth to kidnap human children to increase the Flymen population. They hide inside a Traverser to make the return journey to Earth.

Back in the jungle, Toy is now the new leader. While attempting to kill a large seed-shaped "suckerbird", the tribe accidentally become passengers on the suckerbird. After a long flight, they crash on the coast at the base of a "termight" castle on a peninsula. Walking back to the forest through "Nomansland" – the lethal interface-area between land and sea, Gren is waylaid by a "morel", a sentient fungus which attaches itself to his head and forms a symbiotic relationship. After a power-struggle, Gren leaves the tribe with his girlfriend Poyly, also taken over by the morel.

On their travels, they meet Yattmur of the Herder tribe, who live in caves in a congealed lava bed. At the "Skirt of the black mouth", an unknown creature with Siren-like capabilities almost leads them to their deaths. Escaping, they meet the Tummy-belly men, some of whom they free by cutting the umbilical cords by which they are attached to a parasitic tree. All board a boat belonging to the tummy-bellies, but during the escape Poyly is killed. The boat, uncontrolled, floats downriver into the sea. After several adventures, the crew find themselves on an iceberg, the boat destroyed, after which the berg abuts a small islet. They leave by hitching a ride on a plant which propagates by using self-propelled, stilt-walking seeds, which instinctively walk to the mainland.

They find themselves at the terminator, the boundary between the day and night sides. To their horror, they realise they are being carried over it. After a long journey, the seed stops near the top of a mountain, which is tall enough to still be lit by the low sun. There, Yattmur gives birth to Gren's child and they meet the Sharp-furs. They meet the Sodal Ye and his three helpers. Gren, increasingly taken over by the morel, wants the baby to host it as well. In return for food, the Sodal Ye thinks of a way to remove the morel from Gren's head by coaxing it into a bowl.

They decide to accompany the Sodal Ye back to Bountiful Basin, an arm of the sea close to the terminator. On the way they witness a solar flare. The morel explains to them that the world is about to end as the Sun brightens, and the strange, green columns they begin to see beaming into space is life itself, transferring to new stars.

Followed by Sharp-furs and others, they notice a traverser has landed and blocked the passage to their destination. This is the traverser that was carrying Lily-yo and companions. The morel manages to take over the Sodal Ye and when they reach the giant spider, Gren meets Lily-yo again. They board a traverser which is going to lift off to the stars (after being taken over by the morel which has now divided) – all except Gren, Yattmur, and the baby, who decide to return to the familiar forest - for the end of the world, while soon, will not occur within any of their lifetimes.