The log had been dry for several seasons. Its surface held a firmness that allowed for consistent crossing. Creatures passed over it without hesitation. That was established.

On the third morning after light rain, a small section of the log appeared darker.

Harlan paused at the near end and examined the change. “Moisture retention,” he said.

Della approached from behind. “Temporary?”

Harlan placed one foot on the darkened section and applied pressure. The surface yielded slightly. Not collapse. Yield.

“Noted,” he said.

The spider, positioned above on a low branch, lowered himself several inches on a single thread. “Surface condition altered.”

The darkened area was not large. It occupied a space no wider than a paw and extended only a short distance along the grain. No boundary marked its edge. It transitioned gradually from dry to damp.

Della stepped forward and placed one foot onto the section. She held it there. “It does not reject,” she said.

Harlan removed his foot and observed the faint impression it left behind. The surface did not return immediately to its previous shape. “Retention,” he said.

The spider considered this. “For whom?”

No one answered.

They continued across, each adjusting slightly, distributing weight differently than before. Crossing required attention now, though not difficulty.

By midday, the darkened section had deepened in color.

“It is increasing,” Della said.

Harlan returned to the log and measured the change against a small mark in the bark. “Expansion confirmed.”

The spider descended further. “Cause?”

Harlan examined the underside of the log. No water pooled beneath it. The ground remained as it had been. “No external source,” he said.

Della leaned closer to the surface. A fine green texture had begun to appear, barely visible unless viewed at an angle. “Addition,” she said.

The spider moved laterally along his thread, adjusting his vantage point. “Not addition. Replacement.”

They observed in silence.

The green did not spread quickly. It extended by degrees, each shift requiring attention to notice. Where it had taken hold, the surface was no longer simply damp. It had changed character.

Harlan stepped onto it again. His footing held, though differently. “Friction altered,” he said.

Della placed her foot beside his. “Temperature reduced.”

The spider withdrew upward. “Classification pending.”

They left the log and returned at intervals throughout the afternoon. Each time, the green had advanced.

By dusk, it occupied nearly half the crossing.

The dry portion remained unchanged. It ended abruptly now, where the green began.

Della stood at the boundary and looked down. “Division established.”

Harlan did not respond.

The spider descended once more, stopping just above the surface. “Does it stop?”

No one answered.

They waited.

The green did not pause. It did not hesitate at the boundary. It moved into the remaining dry section without variation in pace.

“The moss,” Della said.

Harlan nodded once. “Designation accepted.”

The spider considered the word. “Behavior?”

They watched as the moss extended another small measure along the grain.

“It continues,” Harlan said.

“For what purpose?” the spider asked.

No one answered.

The next morning, the log was entirely green.

Crossing was still possible. It required adjustment.

Harlan stepped onto the surface and shifted his weight forward. The moss compressed and held. “It supports,” he said.

Della followed. “Condition updated.”

The spider remained above, observing. “The moss will not attend,” he said.

“Why not?” Della asked.

“It is already here.”

They stood in silence.

The moss did not argue. It did not apologize. It did not accelerate. It simply remained.

And slowly, without announcement, it advanced another inch beyond the log and into the soil at either end.

Harlan stepped onto it again, more carefully this time. He adjusted his footing. “It is navigable,” he admitted.

Della sat down. “It is now.”

The Bureau opened a file titled:

Gradual Encroachment — Damp Division

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