These are some figures I culled from Arthur Chapman’s excellent Numbers of Living Species in Australia and the World. The numbers speak for themselves really.
|Taxon||# Known||# Estimated||% known||# To Do||% of Problem|
|Plants (excl. Algae)||297,857||390,800||76.22||92,943||0.98|
I have highlighted in blue the percentages for which DNA barcoding of some form is either a working tool already or likely to be the only practical solution i.e. more than 99% of unknown species. It is hard to imagine the micro algae yielding significant morphological characters ahead of some useful bar coding regions being developed.
Of course one could argue that this isn’t worth doing at all. There is no reason why we have to catalogue every species. Why would one want to create another ten million latin binomials?