4' 2 Joiinial of Agriculture. [8 July, 1908. 



getting accidentally mixed with the others. This difference might be due 

 to a variation occurring naturally or to a natural cross. In a natural 

 variation, the progeny might either revert to the original type, or the varia- 

 tion might be repeated generation after generation and become permanent, 

 when it would be regarded as a " sport." In the case of a natural cross, 

 there would be in the second or variable generation, quite a multiplicity of 

 forms and not a smgle variation as in the so-called " spoTts." Which of 

 these three alternatives is to be accepted? At Svalof the differences were 

 regarded as being due to natural crosses, as the splitting up of the hybrids 

 afterwards was proved by special experiments. 



There are some, however, who maintain that it is impossible for a 

 cross to occur except by artificial means from the very structure of the 

 ear of wheat, and there are certainly a number of obstacles to be over- 

 come before it can take place. Still in cases where from any cause the 

 flower fails to be fertilized by its own pollen — whether from the anthers 

 proving aborti\e or the pollen unfertile — natural crossing does occur and the 

 Thrips is probably the unconscious carrier of the pollen. To test this, 

 Farrer emasculated all the flowers of an ear while the anthers were still 

 quite green and left the flowers exposed to impregnation from the outside. 

 The result was that 84 per cent, of the flowers contained seeds. Natural 

 crosses have been recorded bv accurate observers such as Dr. C. E. 

 Saunders of the Central Experimental Farm, Ottawa, and Rimpau, a 

 famous breeder of cereals, still although so rare it is a wise precaution in 

 crossing, to protect the florets operated on, both before and after the appli- 

 cation of the pollen. 



Deterioration or Diminished Yielding Capacity. 



It is a recognised fact that a variety of, yyheat, whether produced as 

 the result of careful " selection " or by means of " crossing "' has a 

 tendency to degenerate in course of time, tO' lose its pristine \igor as shown 

 by a diminished yield. And an important point to settle is, having secured 

 a good strain, how is it to be maintained in full vigor and prevented from 

 deteriorating or " running out " as it is callied. It is not a question so 

 much of improving the type as of keeping it up to the standard. 



If one knew in each case the cause of this deterioration, then it would 

 be a guide to the best methods of counteracting it, but unfortunately at 

 present we can only surmise. When new breeds are produced by artificial 

 fertilization, for instance, the original vigor of the cross deteriorates under 

 ordinary cultivation and in a few years the yield decreases. This is sup- 

 posed to be due to the continual in-and-in breeding in the case of wheat 

 and the remedy evidently lies in renewing the cross. In order to arrest this 

 diminution in vield, individual florets are selected for crossing each year, 

 and a stocx; is raised from the grain produced by repeating the cross, which 

 is called bv Garton, who has adopted this method, " Regenerated Stock." 

 Various tests have been made under similar conditions with seed from the 

 Original Stock and that from the Regenerated Stock and in every instance 

 the vield was increased, sometimes even to the extent of 25 per cent, in 

 the case of oats. 



This seems at first sight to- ba a very successful method of maintaining 

 the standard of efficiency, but it does not show by anv means that in-and-in 

 breeding is the sole cause of the falling off in yield. It is rather a reflec- 

 tion on the efficacy of crossing that it requires to be repeated so soon. 

 In fact it is evident that there are various causes for the deterioration and 



