Cultivated Grains 



307 



the depth of covering, if the seeds are covered deeply, 

 it will grow to within about one or two inches of the sur- 

 face before forming the permanent roots. It will thus be 

 seen that deep covering of grains does not make the plants 

 deep rooted, and only seems to reduce their chances of 

 success (If 32). The root system of cereals is composed 

 altogether of slender, much branched roots. There are 

 no heavy tap roots as in alfalfa. (See Figs. 32 and 203). 



442. The Best Varieties of Cereals are strains that 

 have been continuously and carefully selected and thus 

 acclimated in the climatic belt in which they are to be 

 grown. High yielding varieties of corn and wheat from 

 moist climates usually give lower yields in dry climates 

 than acclimated native sorts; corn and other grains from 

 dry climates, however, will sometimes out-yield native 

 strains in moist cli- 

 mates, if the change 



is not too radical. In 

 many sections of the 

 South, seed corn is 

 purchased from the 

 North, with the idea 

 that it will give earlier 

 maturity and therefore 

 larger yields. It does 

 give earlier maturity, 

 but it has long been 

 established that im- 

 proved native varieties 

 give more bushels of 

 corn. (See Fig. 188.) 



443. Improvement 

 of Varieties. Nearly 



Fig. 196. Diagram of germinating corn when 

 planted at different depths. 1, when planted 1 

 inch deep ; 2 , planted 3 inches deep ; 3 , planted 

 5 inches deep; c, seedling roots; a, permanent 

 roots ; and b, first internode the length of which 

 is determined by depth of covering of seed. 



