16 FIRST BOOK OF GRASSES 



lowermost leaves of a culm, especially in bamboos. 

 Blades may be flat or folded (often called con- 

 duplicate) or involute; that is, rolled lengthwise. 

 Rarely the inroUed edges are grown together, so 

 that the blade really has no upper surface. Such 

 leaves are called terete (meaning rounded). Blades 

 vary greatly in size, shape, and texture, smoothness 

 or hairiness. In broad leaves there is sometimes a 

 narrow neck, or petiole (leaf -stalk), between the 

 sheath and the blade. 



SUMMARY 



Grasses are distinguished by jointed, round or 

 flattened, usually hollow, cubns, with solid nodes; 

 2-ranked leaves, composed of sheath and blade, 

 with a ligule at their junction; and by the spikelets 

 with 2-ranked glumes and florets. 



EEVIEW 



(1) How is a grass distinguished from all other plants? 



(2) Break a cornstalk and note the arrangement of the torn 

 fibers standing out of the pith. Compare this with the cut end 

 of any twig of a tree or shrub. Cut across a wheat, oat, or rye 

 straw and compare with the cornstalk and with the twig. 



(3) Examine the culm (nodes and internodes) above and below 

 ground and leaves (sheath, ligule, and blade) of any available 

 grass. 



(4) How is a rhizome distinguished from a root? 



(5) What is the difference between a rhizome and a stolon? 



