PART II 

 DEVELOPMENT OF PLANTS 



CHAPTER V 



CLASSIFICATION OF PLANTS 



59. The Method of Classifying Plants. — We have now arrived 

 at an understanding of the nature of the plant and the work 

 which it performs. In this study the most complex forms have 

 been largely considered. There are, however, a great variety of 

 very simple forms ranging from single-celled plants that often 

 form the green coatings on trees up to the complex types. How 

 have these different forms come about and what relation do they 

 sustain to one another? We will also be interested to compare 

 the life histories of these different forms and their modes of life. 

 In approaching this subject it is first necessary to gain a knowl- 

 edge of the system employed in grouping or classifying plants. 

 Obviously many plants are closely related as the red, white, 

 scarlet oaks. Such a group of closely related plants is called a 

 genus (plural, genera) and the different kinds of individuals 

 which compose the group are known as species. The red oak is 

 one of the species of the oak genus. In scientific work the Latin 

 or Greek names are used to designate the genera and species. 

 In the case of the oak the genus is known as Qucrcus, an old 

 Latin name for oak, and the red oak species as rubra, mean- 

 ing red. Both the name of the species and the genus are em- 

 ployed in naming a plant and consequently the scientific name of 

 the red oak is Qnercus rubra. So in other cases we can say white 

 oak or Quercus alba, scarlet oak or Qnercus coccinea, etc. The 

 oak has several characters in common with the chestnut and 

 beech nut genera, as for instance the fruit in each case is asso- 



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