FYI, here's a follow-up shot of last year's Black Mission air layer that I was initially worried might have been too big to root successfully. I cut it from the mother tree as soon as the leaves fell, and planted it in this Costco pretzel jar. Normally the transparent plastic is shaded by a layer of corrugated cardboard, and it sits in a shallow tray filled with an inch and a half of water to keep the young root system from drying out. New root growth is already spreading out against the sides of the "pot".
Great fun--nearly instant gratification, compared to waiting for cuttings! Thanks Jon and others for the great info about air layering. I'm looking forward to trying it again on some of my little figs (last year's UCD cuttings) later in the season, once they're in the ground and better established.