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 acew; the 
rose family, for instance, are the Rosacew; the pink family, 
Caryophyllacee; the walnut family, Juglandacee, 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 Tpomea purpurea. The small 
differences that arise within a species as to the color and 
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