94 
Journal of Agricultural Research 
Vol. II, No. 2 
Fig. 6 .—Eremocttrus glauca: A 
hair from the leaf of a plant 
grown from seed from near 
Chinchilla, Queensland (S. P.I. 
No. 29660). Shows abrupt 
bend near the base and the 
cuticular prominences. Such 
hairs are usually 2- to 4-septate. 
X372. Drawn by Theodor 
Holm. 
and lower surfaces very similar in appearance and function, a not un¬ 
common characteristic of desert plants. The leaves are very thick, 
perhaps because of their double equipment of palisade tissue. The young 
leaves have a scattered covering of minute short, thick appressed hairs, 
with a warty cuticle. They bend abruptly at right angles near the 
base and are from 80 to 135 /£ long and 10 to 16 
H wide, often unicellular when young, but usually 
2- to 4-septate when old. The wall is thickened 
internally at the base where it is bent, and the 
cuticle shows numerous wartlike, oval promi¬ 
nences (fig. 6). These hairs often disappear almost 
entirely from old leaves. Exactly similar hairs 
occur on the young twigs. No such persistent 
coating of hairs occurs on the leaves of any 
other citrous fruit. It is probable that a study 
of this plant in the field will show that this coat¬ 
ing of peculiar hairs serves as a protection to the young twigs and 
leaves as they are developing. 
The young twigs of the Australian desert kumquat are very slender in 
comparison with those of other citrous trees and are, like the leaves, of 
a gray-green color. A cross section of a young twig shows the pres¬ 
ence of a very thick cuticle and small deeply sunken stomates nearly des¬ 
titute of air spaces (fig. 7). Both of these characters indicate strongly 
marked drouth-resist¬ 
ant adaptation. The 
twigs have below the 
epidermis a double 
layer of palisade cells 
filled with chloro¬ 
phyll (see fig. 7) and 
are as well adapted to 
manufacture starchy 
food as are the 
leaves themselves. 
Here, again, we find 
a character common 
in desert plants, 
which often drop their 
leaves in time of se¬ 
vere drouth and utilize their green twigs for as much photosynthesis as 
the scanty water supply will permit. 
That this species must endure severe drouth in its Australian habitat 
is confirmed by the fact that on the day the type specimens were col¬ 
lected Mitchell observed the wilting of some of the Australian acacias, 
themselves drouth-resistant plants. A study of the anatomy of the 
desert kumquat confirms abundantly the natural inference that any 
Fig. 7.—j Eremocttrus glauca: Cross section of the epidermal region of a 
i-year-old twig from near Forestvale, Queensland, collected by T. L. 
Mitchell on October 17, 1846; Gray Herbarium. X248. A, thick- 
walled epidermis, two strata of palisade cells, and inner cortical paren¬ 
chyma; B, a stomate at the bottom of a deep narrow pit. Drawn by 
Theodor Holm. 
