The Book of Grasses 



no part in such service, but if one notices grasses that have been 

 beaten to earth by heavy showers, it will be seen that the lower 

 nodes have lengthened on the side turned earthward, and that the 

 stems are thereby bent upward at sharp angles. 



Sheaths. — The broad, basal portion of each 

 grass leaf is known as the sheath, and, encir- 

 cling the stem, is an important 

 protection to the growing inter- 

 node. Each sheath is usually 

 split, or open, on the side oppo- 

 site the leaf, and the edges of the 

 sheath overlap or partly encircle 

 the stem a second time. In suc- 

 cessive internodes these edges lap alter- 

 nately to right and left, and the rolling of 

 young leaves also alternates in like man- 

 ner. In a few grasses — e. g., Kentucky 

 Blue-grass and Orchard Grass • — the 

 sheaths are perfectly closed at first and 

 are split only as the inflorescence forces 

 its way up. 



Ligule. — At the summit of the sheath 

 is usually a thin membrane, the ligule, which 

 closely embraces the stem and appears as an 

 additional upward growth of the sheath or a 

 continuation of its delicate lining. In each 

 species the ligule is constant in form, some- 

 tim.es consisting of but a tiny ring or frequently 

 appearing as a fringe of hairs. 



Leaves. — Grass leaves are borne alternately 

 on opposite sides of the stem, in what is tech- 

 nically called the two-ranked growth. 



The leaves of a few tropical grasses ap- 

 proach in form those of other families of plants, 

 and in certain species a true petiole is inserted 

 between sheath and blade, but in 

 temperate regions grass leaves vary 

 only in width and length and are 

 always " grass-like," show- 

 ing long, parallel veins • 

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