122 
A COLONY IN THE MAKING 
CHAP. 
acre were obtained, yielding a net profit of over £$ an 
acre. There was little, if any, sign of rust. The next 
year a considerably larger area was put in, and one or 
two new varieties of rust-resistants, notably Bobs and 
Rietti, were put in in small portions. This year the 
Gluyas was considerably affected by rust, the Bobs 
hardly injured, and the Rietti untouched. The crop 
as a whole yielded another satisfactory profit. The 
third year the area was planted principally with Rietti, 
partially with Bobs and Gluyas. The Gluyas was very 
badly affected and the Bobs considerably damaged, 
while even on the Rietti spots of rust began to appear. 
This history, though not a definite one, illustrates the 
course the disease appears to take. Each new resistant 
holds out for a period and then finally succumbs. The 
following theory has been propounded to me by perhaps 
the best practical authority in the Protectorate. A 
particular variety of wheat has especial rust-resisting 
qualities. It is sown, and with a favourable season 
resists the insidious advances of the rust fiend. After 
one or more seasons, a time comes when its inherent 
robustness is weakened either by an unsuitable season, 
or by the attacks of some insect pest or by the exhaus¬ 
tion of the phosphates in the soil. It can then no 
longer successfully combat the assaults which always 
continue. The resistance breaks down in certain 
plants, and they act as stepping-stones to enable the 
rust-spores to accustom themselves to the normal sap 
of all the plants of that variety of wheat. When this 
process is thoroughly accomplished, the variety of 
wheat in question becomes worthless in the Protec¬ 
torate. Up to the present the wheat which has made 
the longest and most successful defence is Rietti, which, 
unfortunately, is not a very high-class wheat or one 
