unidentified (rootlets?)

Interesting, could it be a liverwort? It reminds me of the genus Riccia in terms of growth habit and structure. 

21 hours ago, izak_ said:

Interesting, could it be a liverwort? It reminds me of the genus Riccia in terms of growth habit and structure. 

Thanks for the suggestion! I had to look up Riccia. 

The image height of the photo above is about 8 cm; does that help?

6 hours ago, paleoflor said:

 

Thanks for the suggestion! I had to look up Riccia. 

The image height of the photo above is about 8 cm; does that help?

I'm no expert on these, but the size sounds about right. R. fluitans grows longer if grown aquatically so they can reach that size. It may not be a liverwort but the forking growth habit of your specimen reminded me a lot of them.