APPENDIX 

 SYSTEMATIC BOTANY 



Taxonomy, or systematic botany, deals with the family 

 relationships of plants in the order of their nearness or re- 

 moteness with regard to a common line of descent. Its chief 

 value is the insight it gives into the course of plant evolution 

 and into the nature of the modifications that differentiate 

 each group from the ancestral type. While it is not ad- 

 visable to spend too much time in the mere identification of 

 species, a sufficient number should be examined and de- 

 scribed to familiarize the student with the distinctive 

 characteristics of the principal botanical orders. 



Principles of classification. — All the known plants in the 

 world, numbering not less than one hundred and twenty 

 thousand species of the seed-bearing kind alone, are ranged 

 according to certain resemblances of structure, into a number 

 of great groups known as families or orders. The names 

 of these families are distinguished by the ending acece; the 

 rose family, for instance, are the Rosacece; the pink family, 

 Canjophyllacece; the walnut family, Juglandacece, etc. Each 

 of these families is divided into lesser groups called genera 

 (singular, genus), characterized by similarities showing a 

 still greater degree of affinity than that which marks the 

 larger groups or orders; and finally, when the differences 

 between the individual plants of a kind are so small as to be 

 disregarded, they are considered to form one species; all the 

 common morning-glories, for instance, of whatever shade or 

 color, belong to the species Ipomea purpurea. The small 

 differences that arise within a species as to the color and 

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