THE NATURAL SYSTEM. 361 



3. POLYGAMIA FRUSTRANEA, those with the marginal flowers 



neutral (473, note), the others perfect. 



4. POLYGAMIA NECESSARIA, where the marginal flowers are 



pistillate and fertile, and the central (those of the disk) 

 staminate and sterile. 



5. POLYGAMIA SEGREGATA, where each flower of the head has 



its own proper involucre. 



6. MONOGAMIA, where solitary flowers (that is, not united into 



a head) have united anthers, as in Lobelia. This 

 order was abolished by succeeding Linnsean botanists. 

 The 23d class, Polygamia, has three orders, founded on the 

 characters of the two preceding classes ; namely, 



1. MONCECIA, where both separated and perfect flowers are 



found in the same individual. 



2. DICECIA, where they occupy different individuals. 



3. TRICECIA, where one individual bears the perfect, another 



the staminate, and a third the pistillate flowers. 

 The orders of the 24th class, Cryptogamia, are natural, and 

 therefore indefinable by a single character. They are, 



1. FILICES, the Ferns. 



2. Musci, the Mosses. 



3. ALG^E, which, as left by Linnseus, comprised the Hepatica?, 



Lichens, &c., as well as the Seaweeds. 



4. FUNGI, Mushrooms, &c. 



CHAPTER III. 



OF THE NATURAL SYSTEM. 



685. THE object proposed by the Natural System of Botany is 

 to bring together into groups those plants which most nearly re- 

 semble each other, not in a single and perhaps unimportant point 

 (as in an artificial classification), but in all essential particulars ; 

 and to combine the subordinate groups into larger natural assem- 

 blages, and these into still more comprehensive divisions, so as to 

 embrace the whole vegetable kingdom in a methodical arrange- 

 ment. All the characters which plants present, that is, all the 

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