INTRODUCTION 5 



plants something like the familiar ones. Conse- 

 quently, many common names are used in different 

 parts of the country for widely different plants. In 

 Illinois "June-grass" is Kentucky blue-grass {Poa 

 pratensis), a valuable pasture grass; in Maine "June- 

 grass" is Danthonia spicata, an almost worthless 

 little relative of wild oats; and in parts of the West 

 it is Koderia cristata. The name "blue-joint" is 

 used for three very unlike grasses. On the other 

 hand, many plants have different names in separate 

 parts of the country. Around Washington, D. C, 

 for example. Azalea is commonly called "honey- 

 suckle." Many economic plants (such as potato, 

 turnip, and rye) have common names imiform in 

 any one language but different in distinct languages. 

 When the Latin name of a plant is used, it is definitely 

 imderstood not only throughout the United States 

 but throughout the world what species is referred 

 to. However, the primary reason for using the 

 botanical names is that these indicate the relation- 

 ship of the plants. All plants of a kind have the 

 same genus (or generic) name. [Genus is the sin- 

 gular, genera the plural, generic the adjective.] 

 Kentucky blue-grass and all its kind are Poa: P. 

 pratensis, P. trivialis, P. annua, P. Sandbergii, and 

 so on. The comnaon names of these, Kentucky 

 blue-grass or June-grass, rough meadow-grass, spear- 

 grass, little bunch-grass, respectively, give no clue 

 to their relationship or kind. Knowing Poa pratensis 

 anyone hearing of any grass named Poa has an idea 



