254 CHAPTER XIV 



has shown to be the best for the region, and should try the 

 new varieties only experimentally." 



The main points to be kept in mind in breeding wheat 

 are : — 



(1) Drought Resistance. — Some varieties resist drought 

 better than others — e.g., the durums ; while others are drought- 

 evading because of their early maturityr— e.(/., Gluyas Early. 



(2) Rust Resistance. — Immunity varies with the varieties, 

 some evade rust by early ripening. On the whole, the 

 question of immunity to rust is really little understood. 

 Varieties have been known to be rust-resistant to a marked 

 extent for several years in the Union — e.g., Bob's Rust Proof 

 — Hnd subsequently suddenly to lose w^hat immunity they 

 appear to have had. 



(3) Strength of Straw. — Varieties vary markedly in this 

 respect, and those having weak straw are apt to be " lodged " 

 or laid badly, the straw lying on the ground or nearly so. 

 When this occurs naturally the crop is very much diminished, 

 through discoloured and sprouted grain ; and , of course , a great 

 deal of ditiiculty is experienced in harvesting lodged wheat. 

 Lodging is best seen after pelting showers or in very windy 

 weather. It may be due to the inherent weakness of the 

 straw of certain strains where the " hypoderm and mechanical 

 tissue round the vascular bundles are reduced and their indi- 

 vidual cells comparatively small and thin-walled. Where the 

 straw is weak, the lower internodes are usually bent or broken 

 when lodged." On the other hand, lodging may be caused by 

 the weakness of the roots or by a root system having a poor 

 anchorage on the soil. " Where the root only is at fault, the 

 plant goes down as a whole, the straw being rigid and stiff. 

 The peculiar arrangement of the root-system and the strength 

 of the individual roots which are hereditary characters of dif- 

 ferent varieties of wheat, have a great influence upon the 

 lodging of the crop. 



" In short-strained winter wheats of the Square-hoad type 

 the bases of the straws, just above the ground, bend outwards 

 in the form of a cup, and from their low^er nodes arises a 

 spreading system of adventitious roots ; the first inch or two 

 of the roots below the surface is somewhat rigid and thick- 

 ened considerably, and the cell wall of their tissues strongly 

 lignified. By this spreading arrangement of strong roots the 

 plants are firmly anchored to the soil and prevented from being 

 laid except by the severest storms. 



