414 Hill and Freeman . — The Root-Structure 
I think, a forest district, but it is in the “Acacia zone,” 
i. e. scattered trees of Acacia at 20 to 30 feet apart and the 
colour of the soil showing through a scanty sedge and grass 
sward. Game is abundant in the neighbourhood, man is 
absent. The climate is very dry, but there is probably under- 
ground water within 20 feet of the surface. There may be no 
rain for nine months or so.’ 
In the material at our disposal the thick roots possessed 
spines which varied in their characters according to the state 
of their development. The youngest, although often fully 
grown, were quite soft and gradually tapered off into a fine 
termination bearing rootlets in the ordinary manner ; others 
were quite hard and sharp. The question which here arises is 
whether the normal root-ending of some of the softer spines 
represents a normal condition or not. It will be borne in 
mind that the large spine-bearing roots are, in the natural 
state, aerial ; and the possibility is not excluded, indeed it is 
very probable, that under these circumstances the spines when 
above ground do not terminate in a normal root ; this con- 
dition only obtaining when the organs are buried. 
It is not possible to clear up this point here, inasmuch as 
the necessary evidence is as yet wanting. However, dealing 
with the roots at our disposal, it is seen that the absorbing 
end of the spinous root sooner or later drops off, leaving 
behind a perfect sharply-pointed spine. This may be ex- 
plained either on physical or physiological grounds. It was 
noticed that on dropping into clove oil a spine which had not 
yet lost its apical region, it immediately curled up at the tip, 
became brittle, and on being touched separation took place 
between the absorbent tip and the thick basal part. Some- 
thing similar to this may occur naturally in the buried roots, 
although it is much more probable that the absorbent tip 
shrivels up hopelessly during the dry season. On the other 
hand the breaking may be due to the cutting off of food- 
supplies, for the cortex generally has a withered appearance 
before the actual severance takes place. And further, the 
sieve-plates in the basal parts of the spinous roots were 
