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 



