SOLANUM TUBEROSUM 



517 



roots. Rosa (xo) determined that the rapidity with which 

 potatoes sprout is related to the maturity of the tubers at the time 

 of harvesting, and noted that those harvested while immature 

 emerge from dormancy more slowly than mature tubers. He 

 also found that "The primordia of the vegetative sprouts develop 

 during the later stages of tuber growth, as well as during the 



Fig. 2.73. The root of mature plant showing extent of one-half of total root system. (After 

 Weaver, Root Development of Field Crops, McGraw-Hill Book Co.) 



dormant period." The bud primordia are present even in very 

 young tubers and there is a meristematic region, but the sprout 

 does not begin to form until the later stages of tuber growth. 



The Root. — Plants grown from seed develop a slender tap root 

 from which lateral branches arise to form a more or less fibrous 

 system. (Fig. X73.) Those grown from tubers have a fibrous 

 system consisting of adventitious roots that arise in groups of three 

 at points just above the nodes of the underground stem. The root 

 has been described by Weaver (i8), who states, 



