No. 5. DEPARTMENT OF AGRICULTURE. 399 



TABLE 3. 

 GAIN FROM TUBER SELECTIONS OF POTATOES. TWENTY SELEC- 

 TIONS PROM TWO HUNDRED SEVENTY-FOUR SELECTED TUBERS IN 

 1912. 



Yield of parent variety, 



Av. yield of selections, 



Average gain 



Highest gain 



Av. gain of the best five in 1914, 



1913 

 Ten bill plats. 



10.3 lbs. 

 14.5 lbs, 

 42.0 % 

 103.4 % 

 60.2 % 



1914 

 Rows sixty- two feet. 



91.8 Bu. per A. 

 118.7 Bu. per A. 

 27.0 % 

 47.4 % 

 44.3 % 



Plants which are cross fertilized are usually quite difficult mater- 

 ial with which to work. From the fact that two individuals are 

 concerned in fertilization and seed formation, and that the same has 

 been the case indefinitely, it is easy to see that the individual plant 

 is really a collection of the characteristics of many plants to a 

 greater or less degree. The difficulty of controlling pollination is 

 not a small one, and this having been accomplished frequently with 

 pollen of the kind desired, and in case fertilization does take place 

 the plant may or may not show the desired combinations. It is true 

 that in some cases of cross breeding, we get a blending of the char- 

 acters of the respective parents, while in others only one pareut 

 shows its influence on the progeny. 



It was not until 1900 that anything definite was generally known 

 concerning the method by which certain characters are inherited. At 

 that time the work of Gregor Mendel, an Agustinian monk, was redis- 

 covered. He did his work with peas and reported it to a society in 

 1865, but it attracted little or no attention at the time and was 

 almost forgotten until 1900 when it was rediscovered. Mendel, as a 

 result of his careful work, which extended over a period of eight 

 years, show how peas possessing certain distinct characteristics when 

 crossed will produce in their progeny certain characters with math- 

 ematical accuracy. His work has done much to place the science of 

 breeding on a firm basis, as well as to stimulate interest in the sub- 

 ject so that today we have Mendelian characters and ratios for both 

 the animal and every gradation from snails and mice to man, includ- 

 ing both the animal and the vegetable kingdoms. The work is faci- 

 nating and its results will ultimately be of inestimable value since to 

 a large extent it makes possible the conducting of breeding work 

 with a considerable degree of mathematical certainty. 



Another fertile field of plant breeding is that of breeding for 

 disease resistance. For example, it is estimated that the leaf blight 

 of the potato diminishes the value of the crop more than .|36,000,000 

 annually. Associated with this is the indirect expense due to preven- 

 tive measures as for machines, fungicides and labor. Again it not 

 infrequently happens that the disease reaches proportions such that 

 it becomes necessary to abandon the industry as was the case with 

 respect to the rust on asparagus. It was introduced into this coun- 

 try in 1896 and in a few years had spread from the Atlantic to the 

 Pacific, in many localities completely destroying the industry. Sprays 

 of various kinds were tried but without positive effect and many 



26 



