582 BOTANY OF CROP PLANTS 



form, and is, as a result, more or less soggy after boiling, is 

 preferred. These characteristics are usually found in po- 

 tatoes which are low in starch and high in protein. In the 

 United States, on the other hand, where probably nine-tenths 

 of the potatoes eaten are boiled, a white, floury, starchy po- 

 tato which is mealy and dry when cooked is demanded for 

 table use. In Germany, table potato standards are more like 

 those in the United States. In general, it is considered that 

 for table use in thi§ country potatoes must contain about 17 

 per cent, or more of starch. As a result of experimentation 

 with 15 American varieties, East says: "It is quite evident 

 then that potatoes having as far as possible a homogeneous 

 flesh and containing as large an amount as possible of cor- 

 tical and outer medullary layers in proportion to inner med- 

 ullary layer, should be of the finest quahty." 



Degree of Maturity and Quality. — Analyses in the United 

 States have shown that the "greater part of the total nitro- 

 gen is developed early in the growth of the tuber, while the 

 starch is stored up later." It was also found that " the starch 

 grains of immature tubers are small in size and few in 

 number." Tubers increase in desirabiHty with maturity. 



Degeneracy of the Potato. — The "running out" of potatoes 

 is a common observation. New varieties are put on the 

 market, are very productive for a varying number of years, 

 then they usually begin to "run out" or degenerate. 



In Colorado, varieties in the mountain districts do not 

 tend to run out, or only very slowly, the tendency apparently 

 being easily overcome by seed selection, while in the Greeley 

 district, on the plains, at an altitude of 4,600 feet, the sexual 

 tendencies and consequent degeneracy seem to overcome 

 other influences, such as selection. At Svalof (Sweden) the 

 opinion is held that in a variety of potatoes "there is no 

 period of old age." On the other hand, degeneracy is be- 



