Some watermelon accessions in the United States Department of Agriculture-Agricultural Research Service (USDA-ARS) germplasm collection show a particular phenotype usually described by breeders as Egusi seed-type.
The classification of these accessions has been confusing because there are references in literature to the Egusi type as belonging to Colocynthis citrullus or to Citrullus lanatus. Colocynthis citrullus has been confused with Citrullus colocynthis and as a result, the Egusi watermelon has been sometimes considered a common name for Citrullus colocynthis.
However, it is important to separate botanically Citrullus lanatus [=Colocynthis citrullus L.] having Egusi phenotype, from Citrullus colocynthis Schrad., a different species (commonly called colocynth), that grows wild in warm and arid areas of Africa and Asia. The Egusi watermelon is commonly known in Nigeria and the Congo as wild watermelon, Egusi melon, or Ibara.