Back at the station Sax spent a lot of time sequestered in the labs, looking at plant specimens through microscopes, running a variety of tests, and talking about the results to Berkina and Claire and Jessica.

“They’re mostly polyploids?” Sax asked.

“Yes,” Berkina said.

Polyploidy was fairly frequent at high altitudes on Earth, so it was not surprising. It was an odd phenomenon— a doubling or tripling or even quadrupling of the original chromosome number in a plant. Diploid plants, with ten chromosomes, would be succeeded by polyploids with twenty or thirty or even forty chromosomes. Hybridizers had used the phenomenon for years to develop fancy garden plants, because polyploids were usually larger— larger leaves, flowers, fruits, cell sizes— and they often had a wider range than their parents. That kind of adaptability made them better at occupying new areas, like the spaces in and under a glacier. There were islands in the Terran Arctic where eighty percent of the plants were polyploid. Sax supposed that it was a strategy to avoid the destructive effects of excessive mutation rates, which would explain why it occurred in high-UV areas. Intense UV irradiation would break a number of genes, but if they were replicated in the other sets of chromosomes, then there was likely to be no genotypic damage, and no impediment to reproduction.

“We find that even when we haven’t started with polyploids, which we usually do, they change within a few generations.”

“Have you identified the triggering mechanism that causes it?”

“No.”

Another mystery. Sax stared into the microscope, vexed by this rather astonishing gap in the bizarrely rent fabric of biological science. But there was nothing to be done about it; he had looked into the matter himself in his Echus Overlook labs in the 2050s, and it had appeared that polyploidy was indeed stimulated by more UV radiation than the organism was used to, but how cells read this difference, and then actually doubled or tripled or quadrupled their chromosome count . . .

“I must say, I’m surprised at how much everything is flourishing.”

Claire smiled happily. “I was afraid that after Earth you might think this was pretty barren.”

“Well, no.” He cleared his throat. “I guess I expected nothing. Or just algae and lichen. But those fellfields seem to be thriving. I thought it would take longer.”

“It would on Earth. But you have to remember, we’re not just throwing seeds out there and waiting to see what happens. Every single species has been augmented to increase hardiness and speed of growth.”

“And we’ve been reseeding every spring,” Berkina said, “and fertilizing with nitrogen-fixing bacteria.”

“I thought it was denitrifying bacteria that were all the rage.”

“Those are distributed specifically in thick deposits of sodium nitrate, to transpire the nitrogen into the atmosphere. But where we’re gardening we need more nitrogen in the soil, so we spread nitrogen-fixers.”