TEE PRESERVING OF PLANTS 437 



botany which may be at hand, and place the outlines or skeleton of 

 the classification on the blackboard. This outline may usually be 

 obtained from the table of contents or the introductory key. Under 

 each heading or group, write the names of one or more familiar 

 plants, in order to fix the system in the mind. The pupil should 

 be impressed with the fact that all systems of classification yet 

 devised are imperfect and more or less tentative, but that they 

 serve a purpose, nevertheless, in arranging and classifying our 

 knowledge. As more knowledge is obtained respecting the kinships 

 of plants, new arrangements of the species and other groups must 

 be made. 



LXXXVII. THE PRESERVING OF PLANTS 



565. If the kinds of plants are to be carefully 

 studied, specimens must be preserved. The plants 

 of an entire region can then be seen, and, what 

 is more important, they can be seen side by side, 

 for comparative study is the only productive method 

 in systematic or descriptive botany. 



566. The plants are preserved by drying them 

 under pressure. These dried and pressed plants 

 are then secured to sheets of large white, stiff 

 paper (Fig. 436), and the sheets are filed away 

 in covers, as leaves of music are placed in a port- 

 folio. The covers are laid flat in a cupboard or 

 cabinet. Such a collection of plants is an herba- 

 rium. 



567. Although the specimens shrink some in 

 drying and flowers often lose their color, these 



