These pictures are reproduced from the United States Department of Agriculture Yearbooks for 1904, 1905 and 1906. They were the first pictures of the newly created citranges. These fruits are hybrids of Poncirus trifoliata and Citrus sinensis, the common sweet orange.
The Rusk developed from an orange flower fertilised with Poncirus trifoliata pollen. All the other citranges shown here (plus another called Rustic) were derived from different seeds of a single trifoliate fruit from one flower cross-pollinated by sweet orange. This hybridization is considered unusual, because Poncirus is often said not to be 'zygotic', which means it does not normally form seeds by sexual fertilisation.
Top row shows trifoliate orange and an immature Rusk citrange.
Middle is mature Rusk citrange,
Fruit is 5.1cms in diameter.
Fruit is 5.5cms diameter.
Fruit is 6.5 cms in diameter.
Fruit is 7.5 cms diameter.
....hybridized a century ago
page updated 11th January 2005
Largest of the new citranges, this Morton is 8.0 cms in diameter.