D INTRODUCTION. 
The twenty-fourth class, Cryptogamia, has five 
orders : 
1. Ferns. 4. Flags. 
2. Mosses. 5. Mushrooms. 
3. Liverworts. 
The Linnasan system is professedly artificial. Its 
sole aim (observes Sir J. E. Smith) is to help any one 
to learn the name and history of an unknown plant in 
the most easy and certain manner. This is done by 
first determining its class and order ; after which its ge- 
nus is to be made out, by comparing the parts of fruc- 
tification with all the generic characters of that order ; 
and, finally, its species, by examining all the specific 
definitions of the genus. 
