"What about tridium?" said Dynamon. "How do you go about looking for it?"
"Electrophysiological tests of all kinds," said Thamon. "I must say this valley doesn't look very encouraging. It looks like burned out volcanic ash. Say! What's that up the valley?"
Dynamon gazed back in the direction of the Cosmos Carrier, and felt an uneasy prickling along his spine. The desert valley floor behind them seemed suddenly to have sprouted some tall bushes. There were possibly a dozen of them standing at intervals of twenty yards. They were too far away—perhaps one eighth of a mile—for Dynamon to see them very well, but they appeared to consist of a score of leafless branches radiating outward in all directions from a small core. It was as if a basket ball was bristling with ten-foot javelins.
"Where did they come from?" Dynamon gasped. "I didn't see them when we walked over that ground a few minutes ago."
"Nor I," agreed Thamon. "I can't imagine where they came from."
Just then one of the bushes apparently moved a few feet as if blown by the wind.
"Good Lord!" exclaimed Thamon. "Did you see that? One of those things rolled forward!"
Then another of the fantastic bushes started to roll, and another, and another. In a moment all twelve of the extraordinary apparitions were rolling rapidly down the wind toward the humans. Dynamon felt the hair on the back of his neck stiffen, and he sprang into action, commanding his soldiers to converge around him.
"Thamon, what are those things!" Dynamon cried.
"I don't know," the scientist replied. "I don't think they can be animals. But they might be rootless nitrogen-feeding plants of some kind. Look! Those branches are covered with long thorns!"