516 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
settlers. They seemed to think that no amount of drying-out could 
kill grass clumps as long as they remained in the ground. To decide 
the question it was attempted to start growth in 200 clumps of sweet 
grass of different varieties growing on zoet-doorn-veld by damping 
and shading. The result proved that 92 per cent were quite dead. 
The average number of seeds that germinated in and near these clumps 
was three. Before the end of the season, however, most of the seeds | 
represented by this artificially induced growth were in turn destroyed. 
Just enough rain fell to start germination, and when they were at 
the tenderest stage of growth the sun scorched them to death. The 
result is that an enormous extent of sweet veld has been destroyed. 
On this farm the sweet veld looks more bke a barren ‘“‘brak” than the 
luxuriant pasturage 1t once was. 
The coarser ‘‘sour’’ grasses (Aristidas) to a great extent escaped 
complete destruction. By their habit of growth the clumps are better 
able to resist drought. The thick fibrous covering just above the 
- ground affords more root shade and is a better absorbing medium 
than the scantier clumps of the finer grasses. It seems to me quite 
evident that these so-called ‘“‘sour”’ grasses are comparatively recent 
invaders from the desert north, where natural selection had long since 
fitted them to resist similar conditions. The native sweet grasses 
not able to adapt themselves to this changed environment are losers 
in the struggle for existence. Therefore is it that all our sweet veld 
is yearly diminishing and the sour veld extending. In fact, it is 
almost impossible to get quite pure sweet veld in Waterberg. Our 
best sweet veld would have been called ‘‘ mixed veld”’ a few years ago. 
In the olden days Waterberg was a sweet-veld district. 
It is in their seeds that one can best see the high specialization 
attained by the sour grasses as drought resistance. Their manner of 
distribution and habit of growth were all evolved understress of water- 
lessness in some semidesert country. Their life history is one of 
those fairy tales of botany that might be of interest even to the busy 
man who has no time to notice. With a body shaped like a torpedo 
and a long tapering tail, they have attained in perfection the tadpole 
shape, which nature finds of such advantage that she has evolved it 
a thousandfold in the highest and lowest forms of life—indeed it is 
probable that from such a shape have all organic forms originated. 
Under low magnification it will be seen that both body and tail are 
thickly studded with sharp stiff bristles growing backward. The 
point of the torpedo is an intensely hard horny spike, sharp as the 
point of a needle with a coronal of harpoon points at its base. The 
seed is thus able to cling to the coats of animals, besides being easily 
moved off by the wind. But these qualities are of more immediate 
value in another direction. It is above all things a penetrating 
machine—how efficient one can judge from the fact that it is often 
