Pod, there's just the moisture in the bag, and rinsing it helps prevent any build up of fungus.Apart from a bit of condensatiuon, you can see what's happening in the bag and by the time the root system develops the cutting is ready to deal with any pathogens in the soil mix.
Sheryl, sorry they didn't take for you. I have the advantage of climate. My lacunosa was posted to me so would have had a few days moistened in the plastic bag. I washed it, put it in a new bag and the root system appeared quite quickly. The best was the NOID I got from my father. I was travelling for a week before getting it home, but luckily through the tropics. I just made sure it got its rinse and plenty of daylight. The roots developed so fast it looked like a bag of spagetti with leaves in it. There were a lot of cuttings in the bag though. As Pod said earlier, moisture and temperature are the main requirements.