578 swingle: new genus of citrous fruits 



The fruits of all of the species of Microcitrus have an acid pulp 

 which is rather disagreeably pungent except in the case of the Russell 

 River lime. However, as the two commonly cultivated species, the 

 dooja and the finger lime, are decidedly more hardy than the lime or 

 lemon, they may prove of use in breeding new types of hardy citrous 

 fruits. A number of hybrids have recently been made by the writer 

 between the finger lime and the common lime (Citrus aurmitiJoUa) . 



The Russell River lime is the only species in the genus that yields 

 fruits of sufficiently good quality to be of promise for culture even 

 without any improvement by cross-breeding or selection. Speaking of 

 this plant F. M. Bailey says, "This new species of Citrus is well worthy 

 of cultivation for its fruit, which is juicy and of equal flavour with the 

 West Indian Lime.'"^ 



So far all attempts to introduce the Russell River lime into culture 

 have failed and the rapid clearing up of land along the Russell River 

 threatens to exterminate the species altogether. It is to be hoped that 

 Australian botanists and fruit growers will not permit this to happen. 



The species of Microcitrus are closely related to the desert kum- 

 quat, Eremocitrus glauca,'' a hardy drouth-resistant shrub native to 

 the semi-arid scrubs of the interior of Australia, and could doubtless 

 be hybridized with it. As the desert kumquat is edible in the wild 

 state and is the hardiest known evergreen citrous fruit, such a hybrid 

 would be of great interest in the breeding of new types of hardy sub- 

 stitutes for the lime and lemon. 



« Bailey, F. M. Queensl. Flora, 1: 216. 1899. 



' Swingle, Walter T. Eremocitrus, a new genus of hardy drouth-resistant 

 citrous fruits from Australia, in Journ. Agric. Research, 2 : 85-100, figs. 1-7, 

 pi. 8. Mmj, 1914. 



