64 PLANT BREEDING. 



are mature most of the stocks grown this second year should be dis- 

 carded. These are again planted, and those averaging poorest for the 

 three years are discarded. Any very promising sorts are now rapidly 

 multiplied for variety field tests. These new varieties are yearly com- 

 pared with the standai'd sorts as to yield of tubers, cooking quality, 

 form, size, and general appearance of tubers ; where wanted for the pro- 

 duction of starch they are tested for the i^ercentage content of starch in 

 the ripe tubers. Several kinds of apparatus for the determination of 

 starch in potatoes have been devised. Other characteristics — as earli- 

 ness, size of vines, and adaptability to certain soils and local condi- 

 tions — are also noted. There has been very much effective work done 

 in the breeding of potatoes by Burbank, of California; Heine, of Sax- 

 ony, Germany; Archibald Finley, of Scotland, and many others. The 

 transformation and constant improvement of this once wild Ameri- 

 can si)ecies is quite astonishing, and forms another remarkable exam- 

 ple of what can be done by intelligent effort in plant breeding. 



BREEDING APPLES. 



The apple will serve as an example of an open-fertilized perennial 

 species the varieties of which do not come true to type from seed, but 

 are propagated mainly by grafting the buds or cuttings on other hardy 

 stocks. AVhile plants of this class require a number of years to bring 

 them to the age of fruiting, and still longer to test their hardiness, 

 quality, and yield, there is the great advantage which comes from 

 propagating from buds or cuttings. There is not the necessity of 

 breeding them to uniformity of type, because the cuttings and grafts, 

 being only a part of the single seminal plant, are all true to type. 

 This is also an excellent example of a plant which has been broken 

 up into very many useful varieties by the discovery of superior trees 

 which have come up accidentally, as along fence rows or about cider 



mills. 



There is considerable variation in plants from seeds of self -fertilized 

 apples grown in orchards where the trees are not near trees of other 

 varieties ; but much more where the trees of different sorts are close 

 together, resulting in cross-pollination by the wind and by insects, 

 and where the seeds are from fruits of flowers which have been cross- 

 pollinated by hand. Many of our good varieties of apples have sprung 

 from seedling trees produced from seeds from self-pollinated flowers 

 or from seeds resulting from natural hybridizing in orchards where the 

 trees of two or more varieties are adjacent. But in systematic work 

 in apple breeding it is believed that more is accomplished with a given 

 expenditure by artificially crossing those better varieties which com- 

 bine the desired qualities, and thus producing many variable plants, 

 any one of which proving of value may be rapidly propagated by 

 grafting or budding for dissemination as a new variety. There is an 

 important advantage in the systematic method of cross-pollination. 



