This is the group of Poncirus trifoliata plants in Harvard University's  Arnold Arboretum, Boston, USA. Three plants, one dead! Taken with fruit developing, July 2003.
Click here for exact location details of this and other Poncirus trifoliata plants.
The garden's database also shows an example of the contorted form, 'Flying Dragon'. If anyone can send me a picture, I will post it here!
Boston, Massachusetts, USA
page re-built 11th March 2009
pdf added 31st October 2010

Published in the 1932 edition of the Arnold Arboretum's 'Bulletin of Popular Information' I have recently come across an article entitled
"Growing Oranges  in Boston"
Click the title above to download a 2.7Mb PDF copy.