Ted Shoemaker writes
Can someone please tell me how many species of plants are estimated to
be living today?

Stewart Robert Hinsley schreef

http://news.bbc.co.uk/1/hi/sci/tech/2082570.stm

Says over 400,000 *known* species. On the one hand, some revisions of
genera are reducing the number of species in those genera (others
aren't, e.g. IIRC, the recent revision of Sarcolaenaceae in Adansonia)
as species are reduced to synonymy. On the other hand, new species are
being discovered at an appreciable rate.

Angiosperms are the most diverse of plants; the other divisions have
well under 100,000 species between them. (28,000 on a site giving
235,000 for angiosperms.)

http://mentor.lscf.ucsb.edu/course/w...lecture_12.pdf

I'm not counting green algae (or other algae, or fungi, or
cyanobacteria) as plants.

+ + +
Quite. There is no definitive figure
Taxon 50: 1089. 2001, Govaerts: 422,127 known spp of seed plants
Taxon 51: 511. 2001, Thorne: 258,650 known spp of seed plants

Thorne has added up figures, while Govaerts was using other forms of math.

Taxon 52: 101-104. 2002, Scotland & Wortley
http://fiordiliji.ingentaselect.com/...v/cw/iapt/0040
0262/v52n1/s11/p101, arguing that the lower estimates are likely to be
correct

What with the backlog of unrevised families there is a high degree of
uncertainty

===
Can that statistic be further broken down, either by phylum or by
geography (how many are native to each continent, for example)?

The Angiosperm Phylogeny Website has estimated species counts for each
family.

http://www.mobot.org/MOBOT/Research/APweb/welcome.html
--
Stewart Robert Hinsley

+ + +
The APG site itself does not have data on this but is linked to
http://www.kew.org.uk/data/vascplnt.html
a Kew database (this was a book before it was a database)
PvR