546 Reading-Course for Farmers. 



comparatively few; some have broad rays, others narrow rays. Some 

 plants are tall, others short. No two plants can be found which do not 

 differ from each other in some noticeable character. They present 

 different facial expressions, the same as do people or cattle, so that 

 we may recognize different individuals apart after we have studied 

 them and made their acquaintance. We know the Ox-eye daisy family, 

 yet we are not accustomed to being introduced to Sam Ox-eye, Jim 

 Ox-eye and John Ox-eye and attempting to recognize their character- 

 istics so that we will know them when next they call. ' This, however, is 

 one of the interesting studies which the breeder pursues. Careful gar- 

 deners learn to recognize the individual plants which they handle day 

 after day the same as the shepherd recognizes the different members 

 of his flock. These ordinarily slight variations which are spoken of 

 commonly as individual variations are what the scientists now call 

 continuous or fluctuating variations. 



All of the individuals of any species, race or variety, whether wild 

 or cultivated, show these individual variations. If we examine the 

 different seedling trees in nursery rows of maple or oak, or different 

 corn or wheat plants in fields of the same race, we will find them to 

 present similar individual variations. In many cases such variations 

 are transmitted by a plant to its progeny in the same manner that 

 many of the individual characters or characteristics of a human being 

 are in part at least transmitted to his progeny. 



Such slight individual variations are the type of variation most used 

 by animal-breeders in selecting to improve the breed. In plant-breeding 

 such individual variations are also used when the breeder is selecting 

 to produce an improved strain of any race. If, for example, the breeder 

 desires to produce a heavy yielding strain of the Pride-of-the-North 

 corn, he would select individuals having the maximum yield, plant 

 these in an isolated place and continue the selection year after year, 

 until a high yielding strain of the variety has been produced. In such 

 a .selection the scientist would assume that there had been no change 

 produced in the type of the race but that the breeder by the selection 

 and isolation of the maximum yielding individuals had produced a 

 family, within the race, of high yielding capacity, this being maintained 

 continually by the selection. If, however, the selection and isolation 

 of the highest yielding plants was discontinued and free intercrossing 

 with inferior individuals was allowed, the mean yielding capacity of 

 the race as a whole would soon be established again. 



A second type of variation is that known to gardeners and horti- 

 culturists as sports and to the scientists as mutations. These are very 



