XX 
THORNS—“ THE RELENTLESS TYRANTS OE THE 
WILDERNESS ” 
iVLL writers on the fiora of Eastern Ethiopia draw 
attention to the prickliness of the trees, shrubs, and 
plants. Thorns occur on the stems, branches, stalks, 
and leaves of many trees. Botanists ascribe to thorns 
useful purposes. Prickles on seeds, especially if barbed, 
aid in dispersal, by causing them to fasten on the bodies 
of passing animals. Spines serve to protect plants from 
being eaten by birds, animals, and insects such as slugs. 
The bow-string hemp, Sanstvieria cylindrical has its 
sword-like leaves tipped with a spine so sharp that it 
readily penetrates leather. The butcher-bird, Lanius 
humeraJis, uses the Mauritian hemp (Agave) as a larder, 
and impales its victims on the sharp tips of the leaves. 
Many succulent plants are armed with thorns, or have 
leaves pointed like bayonets, or edged like saws. 
The great feature of the flora of the Xyika (desert) is 
the specialisation of trees and plants to resist desiccation 
and death during periods of drought. This is effected by 
reducing the surfaces which allow loss of moisture by 
transpiration. In many parts of East Africa there are 
only two rainy seasons, and each is of short duration. 
When water is scarce animals eat succulent leaves in 
spite of the thorns. Elephants and lesser kudus chew 
the thick leaves of the Sansevieria in order to obtain the 
juice which they contain, and drop the “ chewed ” fibre. 
These bundles of chewed fibre, bleached by the sun, are 
found in districts over-run by elephants, and bundles 
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