144 FASM GRASSES OF THE XTNTTED STATES 



or early fall. The seed maj' be drilled, or sown broad- 

 cast and covered by harrowing. 



The distribution of Johnson grass is shown in Fig. 

 28, each dot on the map representing a correspondent 

 who reported it as an important grass in his locality. 

 The map shows it to be confined to those portions of 

 the country where the ground seldom or never freezes 

 to the depth reached b}- the plow. It will be noticed 

 that k well-defined area of Johnson grass extends across 

 the State of Alabama a little south of the centre, turn- 

 ing northward into northeastern Mississippi. Maps 

 showing the distribution of cotton and also of the negro 

 population show this same area in a similar manner. 

 It is due to the peculiar soil of that region. This is a 

 broad, fertile strip of black prairie soil, rich in lime 

 and other plant-food. An examination of the geolog- 

 ical map shows this strip to coincide with the rocks of 

 the cretaceous period. W'ith proper drainage, alfalfa 

 does well on this soU. The same soil occurs again in 

 an enormous area in northern and central Texas, form- 

 ing the famous region of black waxj- soU of that State. 

 Johnson grass is perfe<5lly at home throughout this 

 portion of Texas, but it does not, bj' any means, con- 

 fine itself to these cretaceous soils in the South. 



Few grasses will stand greater extremes of moisture 

 than Johnson grass. It luxuriates in moist soils and 

 along the banks of drainage and irrigating ditches, but 

 is at the same time noted for its abilit}- to resist drouth. 

 It makes ver}- little growth in exceedingly dry weather, 

 but lies dormant, and springs up \'igorously as soon as 

 rain comes again. 



