8 May, 1908.] 1 niprnvcmcui of Cereals by Selection ami Crossing. 289 



Professor Perkins starts from what he calls " Selection Plots " in which 

 the grain 's grown from specially selected individual ears, sa) , to the num- 

 ber of 20 or 30. Each head " possesses in the highest degree the special 

 qualities we are looking for " and receives a special index number, under 

 which its salient features are recorded. In each case small and defective 

 grains are carefully graded out, and the balance sown by hand in rows 32 

 inches apart and a link (about 8 inches) apart in each row. 



At harvest-time the .strains to be retained are determined and the best 

 ears are selected from these as before, for sowing the selection flats of next 

 season. What remains in the selection plots is used for sowing in the seed 

 ■plots, so called because thev supplv the .':eed for the ordinary wheat crops 

 of the farm. 



There is thus an automatic regularity al)Out Selection Plot and Seed Plot 

 which appeals to one's sense of order and method and the Professor is so 

 satisfied that the selection to be effective must be continuous and uninter- 

 rupted, that he even looks forward to the time (not in his lifetime however) 

 when the looth selection will be available. 



This continuous and uninterrupted selection seems a logical conclusion, 

 in order to maintain the standard of excellence and prevent retrogression, 

 for if the selected plants are simply extremes of fluctuating variabilty, 

 then as soon as selection ceased, there would be a retrogression to mediocrity, 

 as Galton called it, and not constancy to type. This view :s forcibly 

 maintained by Perkins when he says : — " We recognize that, as soon as we 

 take our eyes oft' a wheat we have been endeavouring to improve, as soon as 

 we sell it to somebody else, so soon will it begin falling back with ever- 

 increasing momentum towards the old dead level of mediocrity." This 

 was the principle of Hallett in his ])edigree-cultures and the " pedigree 

 cereals " at Roseworthy are based on the idea that the best type of parent 

 has to be selected continuouslv. But some of Hallett's pedigree cultures 

 such as Golden Drop wheat and Chevalier barley still maintain their place 

 as distinct types, even although they have long since passed out of his 

 hands. 



On the other hand the experience gained at the Swedish Agricultural 

 Experiment Station and the practice of Hays at the Minnesota Experiment 

 Station has led to the adoption of the principle of the careful selection 

 (f individual plants and the production of a constant race, by simply isolat- 

 ing them, and multiplying the progeny as fast as possible. The point at 

 issue may be tested b\ retaining the various continuous selections of one 

 variety for comparison, and year after year observing if the earlier selec- 

 tions show a return to " the old dead level of mediocrity." So many of 

 our theories regarding heredity are in the melting pot at present that we 

 require an experimental basis for our practical work. The simple prin- 

 ciple of selection followed by us is to chcxjse single mother-plants to begin 

 with and then to judge of their hereditary value not by their visible marks 

 but by the average value of their progeny. The " centgener power '" of 

 each is determined and this settles their final .selection. This is entirely 

 different from the idea of a pedigree-stock from which the seed necessary 

 for sow'ng is directly produced and has to be con.stantly renewed by selec- 

 tion. In the one case the farmer can multiply the seed just as well as the 

 original breeder, while in the other the production of seed is in the hand? 

 of the one with the original pedigree and all the profit as well. 



The association of characters or correlation as it is called has been 

 specially studied In Professor Perkins and he has been able to show by 



41 •2-2. K 



