"The fruits are small, globose, with six segments." 
"The small globular fruits, the elongate-elliptical, crenulate leaves, and the narrowly subcrenulate-margined, very short petioles separate this New Guinea species very clearly from the other species of Microcitrus.   This is the only species of the genus outside of Australia, and it occurs nearly a thousand miles away from
M. garrawayi, the Australian species of Microcitrus growing nearest to New Guinea."
Quotes from The Citrus Industry, Volume 1.
Note that the above was written before the discovery of Microcitrus papuana in Papua New Guinea, and Citrus gracilis in Queensland.
You will notice there is not much information here on this species.
If you have any more information, or pictures, seeds or budwood available please
e-mail me!
page updated 8nd March 2009
Common Name: New Guinea wild lime
Citrus Industry picture of Microcitrus warburgiana fruit
These photos were sent from the University of California 's Riverside Collection.  At times, their specimen is said to have some dieback, especially on the north, and  possibly due to wind.
This picture of fruit and leaves, from the
University of California, Riverside,
is also reproduced in The Citrus Industry Vol 1 - but not in colour.
Marc Harris, a visitor to the Riverside collection, kindly sent me these pictures of the fruit he collected there.   Scale is marked in millimetres.
As you can see these leaves and fruit match the Riverside pictures very well.
The herbarium specimen text reads:
Undisturbed primary forest, Milne Bay Province.
Medium tree, straight boled 15m tall. Smooth bark, leaves glossy green above, pale green below. Fruit green probably ripening yellow.
The following images are reproduced from a specimen in Canberra Herbarium, collected in 1984.

Riverside Microcitrus warburgiana fruit
Canberra Herbarium Microcitrus warburgiana leaves
Canberra Herbarium Microcitrus warburgiana  fruits
Enhanced old Riverside picture Microcitrus warburgiana fruit
Riverside Microcitrus warburgiana fruit in tree
Riverside Microcitrus warburgiana tree