In both types of feather, the barbules that extend from the barb ramus grow from a single layer of cells, called the barbule plate, on the periphery of the barb ridge.
The largest of the main branches is eighteen feet and nine inches in circumference, and some of the long pendulous branchlets droop over the stream at the foot of the fall where it is gray with spray.
FiloBot mimics these behaviours using sensors in its head—at the tip of the main shoot—which is also equipped with a spool of plastic and a heating element.