October 13, 1905. 



SCIENCE. 



465 



pure recessive or pure dominant characters 

 had been hit upon from the first. 



Biffen's work further indicates that the 

 power of producing a glutinous grain, such 

 as will lead to 'strength' in the flour, is a 

 Mendelian character, following the same 

 laws of inheritance as the bearded or 

 beardless habit or the color of the grain or 

 chaff. Extreme strength shown in any 

 particular wheat can then be picked out 

 and combined with any other essential 

 qualities, such as the yield and the char- 

 acter of the straAV, which distinguish our 

 present varieties of wheat. Of course the 

 inheritance of a quality like strength, which 

 is only relative between different varieties, 

 can not be traced with the sharpness with 

 which such characters as the long-awned 

 bearded type can be followed; still the 

 variation that is, as it were, superimposed 

 upon the 'strength' or 'weakness' repre- 

 senting the inherited Mendelian character 

 is not sufficient to obliterate the evidence 

 of inheritance according to the law. And, 

 of course this variation of individual seed- 

 lings in the 'strong' section above and be- 

 low the degree of strength possessed by the 

 parent, i. e., the inherited character, gives 

 the plant-breeder his opportunity of im- 

 proving such a quality at the same time 

 as he is combining with it the other char- 

 acteristics that are desired in the new 

 varieties. Biffen's work among the wheat 

 hybrids touches also upon another point of 

 special importance to South African farm- 

 ing, where the incidence of 'rust' forms 

 the greatest obstacle of extensive and suc- 

 cessful wheat-growing. The climatological 

 conditions which make for a rust attack 

 have not been worked out, as far as can 

 be judged from the behavior of English 

 wheats in various seasons, together with 

 the prevailing climates in countries where 

 rust is specially prevalent ; a flush of 

 growth in the spring followed by high tem- 

 peratures will favor the disease, but South 



Africa, with its great variations in the 

 amount and incidence of the rainfall and- 

 with its very different temperatures, af- 

 fords a very good opportunity for obtain- 

 ing information on this point. Returning, 

 however, to the question of variety, it iS' 

 generally recognized that relative immun- 

 ity or susceptibility to an attack of yellow 

 rust is characteristic of particular varie- 

 ties, and Biff en finds that such 'immunity'' 

 is a true Mendelian character, recessive 

 and therefore only appearing in the sec- 

 ond generation of hybrids between a rust- 

 ing and rust-proof parent. It is not corre- 

 lated with shape or character of the leaf, 

 but is transmitted from one generation to 

 another quite independently, and can, 

 therefore, be picked out of a desirable 

 parent and combined with other qualities 

 of value in different parents. Here, again, 

 we are dealing with a character that is only 

 relative, for no wheat can be called either 

 absolutely rust-proof or entirely suscept- 

 ible ; the offspring that have inherited im- 

 munity Avill still vary a trifle among them- 

 selves in the degree of their resistance to 

 attack, and in this possibility of variation 

 lies the chance of the plant-breeder to im- 

 prove upon the rust-resisting powers of the 

 varieties we now possess. 



The whole work of the plant-breeder is 

 of singular importance in a country like 

 South Africa whose agricultural history is 

 so recent. Our European crops represent 

 the culminating points of a tradition, and 

 are the fruit of the observation and judg- 

 ment of many generations of practical men 

 working, as a rule, with chance material. 

 The products are eminently suited to Euro- 

 pean conditions, but, as has been seen 

 so often, they fail comparatively when 

 brought into other climates and soils. It 

 follows, then, that in a new country the 

 work of the acclimatizer is one of the neces- 

 sary foundations for agriculture, and this 

 involves a careful study of climatology 



