For some reason the plants on tag ships were always dying. Ships returned to inhabited planets for refueling with the machines intact but with the plants dead. The plant cells had to be replaced. It was not that the actual material was expensive. It wasn't. But the process of getting the strange cells to work together as a new unit was time-consuming and enormously costly. That was where the trouble came. The plant couldn't be fitted together like an engine. Alsint had evolved cells that were far more viable, but the only way to test that was in actual use. He had received permission from the Bureau of Exploration to install his plant in a ship and try it for two years. If at the end of that time the plant was still alive, he had something really worthwhile. The only stipulation was that no one on the ship should know that it was a test, since they might, out of consideration for him, modify the service the ship normally went through. It had to be a true rough, tough test. And he was getting it, in more ways than he had expected. Unless he could stay with his plant for the next year and a half, all his work would go for nothing. He drew his hands out of the fluid. "Do you think I'm trying to run out?" he asked quietly. He had proof that he wasn't, but he couldn't use it. Franklan shrugged. "Honestly, I don't. But I'm not blinding myself to what the others will think." He squinted professionally at the burns and dried the hands with a gentle blast of air. He picked up a large tube and squeezed a substance on them which was absorbed almost instantly. "There. You'll be all right in a few days." "Thanks," Alsint said laconically and stood up. As he went out the door, Franklan called after him. "If I see the captain, I'll tell him I don't think you tried to jump ship. I doubt that he'll ask. As I said, service on this ship is voluntary." Personally, Alsint didn't care what Franklan told the captain. However, he was at a definite disadvantage. Next time they came to a planet, if he were to disappear, nobody would be overly inquisitive. * * * * * The tagging operation was far from complete--seven planets in the system and each had to be thoroughly investigated. Long-range investigation, of course. A tag ship rarely landed, and then only when the planet under consideration seemed extremely desirable for colonization, enough to warrant closer observation. It didn't matter whether it had a breathable atmosphere or not, whether it was ice-bound or blazing hot. These were minor difficulties and engineering ingenuity could overcome them. There were other criteria, and it was for these that they were checked.