Agar is an essential thing to have when genetically engineering ancient plants.
In order to make Agar jelly, you will first need to find some Gracilaria seaweed.
1x Gracilaria seaweed in a furnace = 1x Liquid Agar
Once you have some Liquid Agar, combine it with some Petri Dishes:
4x Petri Dishes + 1x Liquid Agar = 4x Petri Dish with Agar
These will become useful when making plant seeds...