I2 4 



PASTORAL AND AGRICULTURAL BOTANY 



grasses of this sort. The second method of branching has been termed 

 the intravaginal where the new branches grow inside of the sheath 

 parallel to the stem, finally breaking out at the top of the sheath. 

 Such grasses are known as bunch, hassock, or tussock grasses and are 

 characteristic of the western plains, or steppes of the world, where the 

 tufts of grasses are separated by intervals of soil bare of grasses. When 

 the stem of grasses, especially agricultural grasses, such as maize, rye and 

 wheat, are prostrated by a wind storm, they are said to be lodged. 

 No mechanical tissue, which the stem may have, will prevent lodging, if 

 the wind be sufficiently strong. Frequently after lodging, the stem will 



tertiary stem 

 -tcale leaf 

 -secondary stem 

 primary stem 



roots 



< ' gram remains 

 roots 



FIG. 47. Diagrammatic representation of tillering in cereals. (Robbins after 



Schindler.) 



erect itself again, but at an angle. This is in response to the stimulus 

 of gravity (geotropism). There remains on the upper side of each grass 

 stem node a zone of cells capable of growth partly belonging to the 

 enlarged base of the sheath and partly to the swollen node. The cells 

 of the lower side of this nascent area begin to grow and the stem 

 bends upward in response to this growth. The production of a number 

 of new upright branches from the lower nodes of the stem in grasses is 

 known as "mooting," "stooling" or "tillering" (Fig. 47). The individual 

 branches are called "tillers" and the entire mass of branches is known as 

 the "stool." This method of tillering is found in cultivated oats and 



