Thirty 
THE SOUTH AUSTRALIAN NATURALIST December, 1952 
When selective grazing fails to 
afford normal maintenance the 
rabbit falls back on two further 
lines oi defence. The first is reduc- 
tion in energy used for mainten- 
ance without reduction in the 
size and capacity of the digestive 
tract; in this stage the bodies of 
rabbits recede almost to skeletons, 
activity is kept at a minimum and 
anything affording nutrients is 
eaten — bark of living trees, fallen 
leaves, roots, etc. Finally, as F. N. 
Ratcliffe (0 ) has pointed out, most, 
but never all, die, the survivors 
probably maintaining themselves 
on the minimal vegetative produc- 
tion which occurs even under the 
worst of drought conditions. From 
this residue a new population will 
arise rapidly as soon as fodder suit- 
able for breeding becomes avail- 
able over the necessary number of 
generations. 
The general picture is that the 
rabbit has fitted its reproduction 
successfully to the pattern of pas- 
ture growth in our Mediterranean 
type of climate; where an intense 
flush of spring growth is followed 
by a summer drought which re- 
duces the pastures to little but 
standing straw. Each spring large 
numbers of young can be raised, 
sufficient to replace any severe 
depletion caused by environment 
and its natural enemies including 
man, and to recolonise promptly 
any accessible areas from which it 
has been eliminated. 
References. 
( J ) Evans & Bishop, J. Amer. Med. Assoc., 
81; 889 (1923). 
( 2 ) Page, Dennis. Emp. T. Exptl. Agric. 
10; 103 (1942). 
( 3 ) Eden, A. Nature. 145: 36 (1940). 
( 4 ) Minchin, A. K., Records of South 
Australian Museum. 6: 1 (1937). 
( 5 ) Hellberg, A. Kg Landbrukahad 
Veternskajo No. 5, Almquist and 
Wiksells, Uppsala, 1949. 
( 6 ) Ratcliff e, F. N., “Flying Fox and 
Drifting Sand/’ Melbourne. 1938. 
WEEPING FORM OF EUCALYPTUS SPECIES 
Continued from page 20. 
All the lower branches have pro- 
duced numerous vertically pendu- 
lous limbs which now form a 
“skirt” around the tree. On exam- 
ination, other trees in the same 
valley show the same variation, 
which is amongst the most re- 
markable seen. It is to be hoped 
that these trees, the writer's atten- 
tion to which was drawn by Mr. H. 
A. Lindsay, w ill be preserved under 
such legislation as has been en- 
I visaged by the National Trust Bill, 
introduced into Parliament last 
year. 
In addition to these habit forms, 
various other species have pro- 
duced variegated forms. In rare 
instances these have been propa- 
gated successfully by budding, but 
seedlings raised from seed pro- 
duced by these plants have all re- 
sulted in green plants. — T.R.N.L. 
