Seeking names for four wild plants

I've attached eight pictures in total; each of the four wild plants has two pictures. All of the plants were found in central Florida.

 

I only had time for a quick look, but try these...
#1 Ludwigia sp.
#2 Poinsettia sp. maybe P. cyathophora
#4 Ambrosia sp.

 

#3 is some sort of Malvaceae

 

Might find #2 under Euphorbia cyathophora

 

Yes #2 appears to be Euphorbia heterophylla or E. cyathophora, a noxious weed in Florida, listed as E. prunifolia (synonym):

http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?16374

See this earlier thread:
http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=4249

You can see the similarity to poinsettia, Euphorbia pulcherrima.

 

I just found this site, which might help you in your quest to identify native plants in your area...
http://www.wildflphoto.com/plistwt.htm

 

I agree with Euphorbia cyathophora Murr. being the likely plant for the second plant (third and fouth images). For the fourth plant (seventh and eighth images), Ambrosia psilostachya DC. or Ambrosia artemisiifolia L. is the likely plant. Thus far, I am unsure of the first plant and third plant; I'm still looking through species of Ludwigia (likely the first plant).

And that web site you mentioned is nice; I recognized a few plants straight away; I'm still browsing through the pictures (several hundred).

Thanks, tipularia. :)