Answer: Good thing you asked! Some seeds need darkness to germinate, others require light. The polythene simply means a plastic bag. A clean, transparent plastic bag such as those drycleaners use (or kitchen-type plastic wrap or a clean bread wrapper bag or whatever you have handy) is what you want to use UNLESS the packet specifically says to exclude light. The plastic is meant to maintain humidity and a clear or nearly clear bag is the easiest to see through so that you know right away when the seeds begin to germinate so you can remove the plastic promptly. If the instructions say to exclude light, then use a layer of cardboard or some other opaque covering. You could also set the pan in a closet. Just remember to check them for germination! Good luck with your seedlings.
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