21 



alternately on opposite sides of the axis, one above the other, with a 

 pair of empty or outer glumes at the base of the cluster. Such may be 

 seen in the blue grass (Poa pratensis), fescue grass (Festuca) and many 

 others. 



There are innumerable modifications of these floral organs, and upon 

 the differences which exist in them the distinctions of genera and species 

 are based. In some cases the glumes are entire in outline, in some they 

 are toothed and lobed, and sometimes running out into a slender point 

 called an awn, sometimes with a bristle or awn on the back, etc. They 

 also vary in size from the twentieth part of an inch to an inch or more 



in length. 



PLATE 1. 



FIG. 1. 1, fibrous roots ; 4, culm; 5, node; 6, leaf. 



2. 2, rhizoma; 4, culm; 6, blade of leaf; 7, lignle ; 9, scales of the rhizonia. 



3. 1, root fibers ; 3, bulbous base of culm ; 4, culm ; 5, sheath ; 6, blade. 



4. 2, scaly rhizoraas; 4, node; 6, blade; 7, ligule; 9, scales of the rhizoma. 



5. 1, fibrous roots ; 2, creeping rhizoma ; 4, culm ; 5, sheath ; 6, blade ; 7, cnhn ; 



8, nodes. 



PLATE 2. 



The numbers in each of the figures are as follows: 1, sheath ; 2, blade ; 3, culm ; 4, 

 node, or joint; 5, ligule. 

 The ligule is best shown in the lower right-hand figure. 



PLATE 3. 



FIG. 1. A dense spike (Alopecurus pratensis). 



2. An elongated, one-sided spike (Paspalum dilatatum). 



3. Spike (Hordeum prateuse). 



4. Spike (Agropyrum repens). 



5. Spike (Elymus condensatus). 



6. Spike (Bouteloua polystachya). 



7. Spike (Bouteloua oligostachya). 



8. Panicle (Panicum Crus-galli). 



9. Panicle (Agrostis exarata). 



10. Panicle (Kceleria cristata). 



11. Panicle (Distichlis maritima). 



12. Panicle (Bronaus secalinus). 



13. Panicle (Hierochloa borealis). 



14. Panicle (Poa pratensis). 



15. Panicle (Dactylis glomerata). 



PLATE 4. 



FIG. 1. Two spikelets, one closed, one opened, of Agrostis vulgaris. 



2. Two spikelets, one closed, one opened, of Agrostis exarata. 



3. Two spikelets, one closed, one opened, of Sporobolus Indicus. 



4. An opened spikelet of Calaraagrostis Canadensis. 



5. Two spikelets, one closed, one opened, of Phleum pratense. 



6. Two spikelets, one closed, one opened, of Muhlenbergia diifnsa. 



7. Two spikelets, one closed, one opened, of Paspalum dilatatum. 



8. Two spikelets, one closed, one opened, of Paspalum Leve. 



9. A spikelet of Aristida purpurea. 



10. Two spikelets, one closed, one opened, of Setaria setosa. 



