44 THE PLANT: A GENERAL EXTERNAL VIEW 



Fig. I. — The young plant- 

 body of a common weed 

 called lamb's quarters or 

 pigweed. It is composed 

 of roots, stems, leaves, and 

 the buds of flowers. The 

 scientific name of this plant 

 is Chenepodium album.* 



It is the power of transforming cer- 

 tain crude and lifeless substances 

 of the soil and air into those com- 

 plex and Hfe-giving substances on 

 which all life depends. It is the 

 power of using the energy of the 

 sun and thereby sustaining the life 

 of the world. 



D. Organs and Functions. ^- The 

 main divisions of the plant body 

 are root, stem, and leaf. These are 

 the organs of nutrition. The work 

 of any living body is divided among 

 its parts, and these parts are called 

 organs. The word organ implies 

 that work is done ; thus when we 

 call roots, stems, and leaves the 

 organs of nutrition, we mean that 

 the work of nutrition is subdivided 

 among them. The work which an 

 organ does is called it's function. We 



*The scientific names of all plants and 

 animals have two parts. The first part names 

 the genus to which the form belongs, while the 

 second part names the particular kind or 

 species. Thus Chenepodium is the generic name 

 of this plant, and album is its specific name. 

 The plural of genus is genera. Species has the 

 same form in both singular and plural. Genera 

 are subdivided into species, while groups of 

 genera form what are called the families of 

 plants. When only one name is given for a 

 plant, it is the name of the genus. 



