Germination is less easy at this time of year in cooler areas due to reduce temperatures and dewpoint. These plastic containers are on raised staging in my heated polytunnel where the temperature should be sufficient for germination of most palms and cycads at 25-30°C/77-86°F. The containers have a layer of wet gravel to increase humidity, although they are not totally air tight so moisture will be lost gradually. Being fairly clear they allow good light transmission, which is essential for some species to germinate. Being containerized also shields the contents from and sudden temperature changes, caused by draughts when the polytunnel door is open, etc.