241. 
The slender, usually spiny twigs, are also gray-green, and have stomates situated 
at the bottom of deep pits. In all of these and in some other characters the plant 
shows the outward signs of a profound adaptation to withstand the extreme 
dryness of a desert climate." 
(There has been a good deal of argument as to the meaning of the term " desert. 
Where Eremocitrus grows is grand sheep country, and the employment of the term 
desert in regard to such country must be purely technical.) 
At pp. 93-95 of the above paper the drought resistant properties of the species 
are carefully worked out. At p. 95 he concludes, " It is very probable that the ability 
of this plant to grow in dry soils exposed to hot, dry winds will render it of great value 
in breeding new types of citrous fruits better fitted than any we now possess to grow 
under semiarid conditions." 
Utilisation of Eremocitrus in Breeding. I make no apology for copy- 
ing out what Dr. Swingle says (at p. 97) under this heading :- 
" From the taxonomic study of Eremocitrus, it is clear that its nearest relationship is with the peculiar 
Australian species of Citrus (especially ('. australis and C. australasica), with which it shows close similarities 
in many characters of fundamental importance, such as the flower and fruit structure and the method of 
germination. 
" This close relationship, deduced from the botanical characters, is confirmed by the fact that 
Eremoeitruf glnuca grows vigorously when grafted on Citrus australasica (PI. VIII, fig. 1), and that Citrus 
australaxica grafts readily on Eremocitrus glauca. It has been found that Citrus australasica hybridizes 
freely with at least two cultivated species of Citrus,* and it is not only almost certain that Eremocitrus 
glauca will cross with Citrus australasica and the other Australian species of Citrus, but also very probable 
that it will hybridize with the commonly cultivated Asiatic species of Citrus. 
" The desert kumquat, native to the semiarid Australian scrubs, able to withstand severe cold in 
winter as well as burning heat and extreme dryness both of the soil and air in summer, is the most promising 
species known for use in breeding new types of hardy citrous fruits. Every effort is being made to hasten 
its flowering, so that hybrids can be made, using it as one of the parents. The fact that the desert kumquat 
has edible fruits without any disagreeable acrid oil in the peel or in the juice makes it far more promising 
than the Chinese trifoliate orange, Ponciris trifoliata (L.) Raf. (Citrus trifoliata L.), for breeding hardy 
citrous fruits for table use. 
' The discovery of this markedly drouth-resistant species in the Australian scrubs opens the way to 
the breeding of a new class of citrous fruits, able to grow with much less water than is required by ordinary 
oranges, lemons or grapefruits." 
Grafting and Budding Eremocitrus. Dr. Swingle goes on to say : 
' The Australian desert kumquat can be readily grafted or budded on all of the commonly cultivated 
species of Citrus, such as the orange, grapefruit, lemon, &c., and also on the Australian finger lime (C. 
a>ixtraln*ica). It grows very well on the tabog of the Philippine Islands (Chaetospermum glutinosa (Blanco) 
Swing.), and on the wood-apple of India (Feronia ekphantuin Corr.). (See PI. VIII.) 
' The various species of Citrus graft easily on Eremocitrus, which makes it possible to test this new 
hardy stock for types of soil to which the commonly used citrous stocks are not well adapted. It is not 
impossible that the desert kumquat, being adapted to grow in desert soils, which are usually more or less 
saline, will prove able to withstand more ' alkali ' in the soil than the Asiatic species of Citras, which are 
indeed very sensitive to salty soils or water. 
" Being different from Citrus in so many visible characters, it is possible that Eremocitrus will also 
differ physiologically and prove resistant to some of the many fungous diseases that attack citrous stocks." 
Mr. George W. Oliver crossed Citriu auilralasica with C. mitis in 1909, and the writer crossed the same species 
with C. auranlifrfia, the common lime, in 1913, in the greenhouses of the Department of Agriculture at Washington, D.C. 
Vigorous hybrids were secured from both of these crosses. 
