Stigeoclonium farctum:
Germination is strictly prostrate, and an extensive basal system develops, growing in an 'ice-crystal' -like fashion to form a closed pseudoparenchymatous disc. The pyrenoids in the cells are spaced equidistantly from the original zoospore, forming concentric rings.

 

Here are some pictures of cultured Stigeoclonium

   

John Kinross