And as we drove closer to its source I saw that it did indeed pass through a leafy screen hanging over the passage end.

This Rador drew aside cautiously, beckoned us and we stepped through.
It appeared to be a tunnel cut through soft green mould.

Its base was a flat strip of pathway a yard wide from which the walls curved out in perfect cylindrical form, smoothed and evened with utmost nicety.
Thirty feet wide they were at their widest, then drew toward each other with no break in their symmetry; they did not close.

Above was, roughly, a ten-foot rift, ragged edged, through which poured light like that in the heart of pale amber, a buttercup light shot through with curiously evanescent bronze shadows.
"Quick!" commanded Rador, uneasily, and set off at a sharp pace.
Now, my eyes accustomed to the strange light, I saw that the tunnel's walls were of moss.

In them I could trace fringe leaf and curly leaf, pressings of enormous bladder caps (Physcomitrium), immense splashes of what seemed to be the scarlet-crested Cladonia, traceries of huge moss veils, crushings of teeth (peristome) gigantic; spore cases brown and white, saffron and ivory, hot vermilions and cerulean blues, pressed into an astounding mosaic by some titanic force.
"Hurry!" It was Rador calling.