Very interesting material, including images, on a large number of citrus species found at Home Citrus Growers.
I'll add these three links for Citrus enthusiasts. The first link below is a portal to a lot of other links involving Fruit & Nut trees and Citrus. http://fruitsandnuts.ucdavis.edu/crops/citrus.shtml http://homeorchard.ucdavis.edu/Citrus.shtml http://axp.ipm.ucdavis.edu/PMG/selectnewpest.citrus.html Jim
Acorn Springs Farms is a commercial site but it contains a fair amount of information on growing citrus and hosts a forum for these plants.
Have a look here for some very rare citrus varieties. This is a friend of mine in Germany. http://albums.photo.epson.com/j/AlbumList?u=4214778&f=0