"This is an amusing plant," explained the tutor. "It grows wild on Io. You see, it has a resonant diaphragm over which is a natural harp. Each string of the harp has its own pitch. Furthermore, each string exudes a perfume of its own, different from that of any other string.
"The perfumes attract these insects flying about, and they dash themselves against the fibers, causing them to vibrate, producing music. That, in turn, attracts small birds, which are caught and eaten by the plant."
"Neat, but elaborate," commented Winchester dryly.
Shortly afterwards they climbed into a lunabile and struck out along one of the roads. A few minutes later they heard a series of dull booms ahead, as if blasting was in progress. They came to a stretch of road shielded on one side by metallic plates, in which observation slits had been cut every few hundred feet. The bombardment on the other side continued intermittently.
"Floribombs," explained the tutor tersely, in response to Winchester's inquiring look.
He pulled the scooter to the side of the road near a peeping slot and got out. Winchester cautiously put an eye to the hole. A field of liverish-colored soil stretched out before him, dotted here and there with bushes. As he looked, a clump of them blew up with a boom that shook the ground.
When the dust cleared away, there were only ragged holes where the plants had been.
"That is a Mercurian plant — in a double sense," said the tutor. "It comes from Mercury, and it feeds on mercury, as well as nitrogen and water. Now is its seeding-time. The soil you see is a mixture of cinnabar, ordinary earth and some selected nitrate fertilizers. The plant synthesizes some of these elements into fulminate of mercury, which gathers in its seed pods just as the seeds begin to ripen.
"When the accumulation is complete, the least jar will set it off, throwing the seeds for hundreds of yards around. A faint breeze is all that is needed, which makes the plants rather dangerous to have around. We hope to put them to industrial use, but so far no one has worked out a safe way to harvest them."
The instructor stopped talking as another of the plants disintegrated, then went back to the lunabile.
"They appropriate twenty Grade-P slaves a year for experimental use," he added glumly. "But so far, it has resulted only in simple massacres. I am glad they took me off that work." He coughed. "The Khan is great and wise."
"He is the All-Highest," murmured Winchester, shuddering.
They came to a turn in the road, and were passing a group of the gray-clad slaves of the lower grades. Some of them already had on crude suits of armor, while others were still dressing. Armed guards stood over them, urging speed, lest all the plants blow up before they could get out onto the field.
The lunabile drew up before another laboratory building five miles beyond.
"You'll need a gas mask here," warned the tutor, producing a pair of them from a compartment in the car. "This is the Lotusol distillery."
It was not a large building. Winchester found himself in the receiving room. Here several masked slaves were feeding fat, lush leaves to a set of rolls which squeezed the juice out of them. This was drained off into pans and piped into the next room, where there was a series of retorts set over low flames.
A single scientist watched the apparatus here. In the room beyond, glass piping of small bore carried the pale canary distillate to a machine that bottled it in small ampules. More slaves took the ampules away and packed them tenderly into cotton-padded cases.
"Essence of Lotus juice," amplified the tutor, as they emerged. "This distillery runs only now and then. We furnish the police with fifty cases a year. No one else may have it."
"Lotus juice?" queried Winchester. "I thought that was the stuff that made addicts for the Crater of Dreams. Why should they allow it to the police?"
"The police do not take it themselves. They use it to dope the year's selected artists with. It makes them more tractable. Few intellectuals go voluntarily, you know. They cure that by spraying them with an atomizer.
"After a whiff or so, they want nothing else. I saw it done once — to a designer of ballet dances."
He stared meaningly at Winchester.
"It was not nice to see," he added softly. "He was my brother."
That time the instructor did not append the stock phrase of glorification to the Khan.
"The practise of botany is not what it used to be," commented Winchester, by way of reply.
"No," snapped the tutor.
In his eyes was a peculiar light.
That night Winchester made out his daily report in the exact fashion directed by the AFPA chieftain at Central. In doing so he took great care to exhibit no curiosity concerning the spot where he wrote. He knew that 8-RYF or one of his minions must be watching him through a cleverly concealed television scanner.
But he was equally confident that if such was the case, it would be so well hidden that no effort of his would find it. He assumed, too, that they did not want him to find out the method of transmission, or they would have told him about it before this.
He wrote sheet after sheet, steadily and without reserve. He put down the substance of the conversation he had had with his tutor. He characterized him as "not openly disloyal, but unenthusiastic." He was reluctant to do that, but he had a shrewd idea he was being tested. It was not unlikely that the tutor was also submitting a report.
Similarly, ten days later, after attending a clandestine meeting of six self-styled rebels — "freemen" all, loaned as assistant gardeners from the labor gangs of Cosmopolis — Winchester reported all that was said. They wanted, the gardeners told him, a certain vegetable oil derived from the flowers of the toxidal, a deadly poisonous vine of Ceres.
They had a fellow conspirator who was an assistant cook in the police barracks at Cosmopolis, and who promised to mix it in the food.
Winchester never knew what followed, as the working party finished its job and was withdrawn a few days later, but he had the feeling he had done no innocent man wrong. His invitation to the meeting, while furtively offered, was too bold. Genuine rebels would not have been so frank with an untested stranger.
CHAPTER XIII
Crater of Dreams
Winchester's testing period stretched into months, and still no word came from the mysterious man in green in the citadel. The American continued to work at whatever tasks were assigned, and learned many startling facts about the weird creatures of other worlds. Not only did he work with plants, but on several occasions assisted in the Zoological Division, and there he had to deal with queer animals.
One of his jobs was to discover a substitute diet for the terrible Venusian sea-tigret, which dwelled on the cliffs above the artificial lakes in the Venus Crater. It was a mammal much on the lines of a seal, but spotted like a leopard and possessing the powerful teeth of a cat, as well as claws at the tips of its flippers.
Its habit was to lie in waiting along the brow of the cliff, then pounce on the prey it could spot in the clear waters beneath. The sea-tigret was fierce and voracious, and the curators found it impossible to keep the lake stocked with suitable fish.
Another troublesome animal was the Ursa Saturnis, or the great bear of Saturn. It was a huge, rotund beast, covered with silky white feathers, on which a scarlet spiral stripe wound like the markings of a barber pole. It did not prey on large animals, but on tiny ones that lived in the crevices of rocks.
That problem Winchester helped solve by suggesting