EREMOCITRUS, A NEW GENUS OF HARDY, DROUTH- 
RESISTANT CITROUS FRUITS FROM AUSTRALIA 
By Walter T. Swingle, 
Physiologist , in Charge of Crop Physiology and Breeding Investigations, 
Bureau of Plant Industry 
A survey of the plants belonging to the orange subfamily (Citratae), 
undertaken in the hope of finding new material for use in breeding, has 
brought to fight a citrous plant which combines in some degree the 
winter dormancy of the kumquat and the absolute cold resistance of the 
trifoliate orange. This is the Australian desert kumquat, originally 
described as Triphasia glauca Lindl. and now called Atalantia glauca 
(Lindl.) Benth. by most botanists. 
A study of the reports of the early Australian exploring expeditions 
has shown that this plant is undoubtedly the most cold-resistant of all 
the evergreen citrous fruits, that it is also drouth-resistant, and yields an 
edible, though small, kumquat-like fruit. With these qualities it com¬ 
bines a high degree of winter dormancy. 
An examination of the scanty material of this plant preserved in the 
herbaria of Europe and America and a study of living plants now growing 
in the greenhouses of the Department of Agriculture at Washington, D. C., 
show that its relationships have been misunderstood by botanists. When 
first described it was wrongly put into the genus Triphasia and is still out 
of place in the genus Atalantia, to which it is now referred. As a matter 
of fact, the Australian desert kumquat is much more closely related to 
Citrus than are either of the genera just named. It is most closely 
related to the Australian species of Citrus and, like them, can in all 
probability be hybridized with the commonly cultivated species of Citrus. 
It can be grafted readily on the common citrous stocks. 
The Australian desert kumquat is in many ways unique. It is the only 
member of the subfamily Citratae that shows marked adaptation to desert 
climates. It is a gray-green shrub or small tree, looking not unlike a 
large, thorny sage bush, having leaves centric in structure, with appressed 
hairs, stomates, and a very thick-walled epidermis on both surfaces and 
palisade tissue just beneath. The slender, usually spiny twigs (fig. i) 
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 heat 
and dryness of a desert climate. 
Because of these unique structural peculiarities and because of decided 
differences in the number, arrangement, and character of the floral 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
(85) 
Vol. n, No. a 
May 25, 1914 
G—19 
