http://www.novalek.com/kordon/breathing_bags/index.htm
Has anyone ever tried these? They are designed for transporting fishes over long distances, but they seem to me like an ideal solution for selective breeding, enabling you to collect pollen and completely pollinate a branch inside a bag that not only lets light in, but allows air exchange.
I guess it's got tiny tiny holes in it, just big enough to allow Oygyen and Carbon Dioxide molecules through, but not water molecules. A water molecule is around 1nm, wheras cannabis pollen is around 30µm, way bigger, so they wouldn't escape.
The bags come in sizes big enough to cover a two and a half foot plant, too, so you could feasibly use them to isolate a male plant in amongst many females in your flowering chamber, instead of "throwing out the males". Just a side-thought.
-mu