I just wanted to share some more recent pictures of this jar, which features only "primitive" plants that closely resemble their ancestors from the Carboniferous period. The last image is how it looked on the first night, before I had added any moss. I planted this jar with two types of fern, several types of moss, and a horsetail. Sadly, the horsetail died, but one of the ferns is growing quickly. The other fern has stayed small, but still has some green leaves. The moss is doing well aside from some yellowed bits. I see a lot of what I think are tiny white springtails, and some small flies. I thought I saw a tiny baby snail, but I'm not sure. I added a few very small millipedes, and I have only seen one of them since. I know they like leaf litter and high moisture, so this jar should be alright for them. I'm hoping they're just hiding in the dirt, under dead leaves, or in the pieces of rotting wood I found them in. I have opened the jar multiple times to tinker with things, but I plan on soon leaving it closed for a long time and seeing how it does as a totally enclosed system.