338 TAXONOMY. 



685. The 23d class, Polygamia, has three orders, two of them 

 founded on the characters of the two preceding classes and 

 bearing their names, and the third named upon the same prin- 

 ciple, namely : 



1. MONCECIA, where both separated and perfect flowers are found in 



the same plant. 



2. DICECIA, where they occupy two different plants. 



3. TRKECIA, where one individual bears the perfect, another the stami- 



nate, and a third the pistillate flowers. 



686. The orders of the 24th class, Cryptogamia, the Flower- 

 less Plants, are so man}' natural orders, and are not definable 

 by a single character. They are : 



1. FILICES, the Ferns. 



2. Musci, the Mosses. 



3. ALG-S, which, as left by Linnaeus, comprised the Hepaticae, Lichens, 



&c., as well as the seaweeds. 



4. FUNGI, Mushrooms, &c. 



687. In its day, this artificial system well fulfilled its purpose, 

 and was preferred to all others on the score of facility and defi- 

 niteness. Now no botanist would think of employing it, nor 

 would it be chosen for a key to genera, which was its only legiti- 

 mate use. 



688. The Natural System was rightly appreciated by Linnaeus, 

 who pronounced it to be the first and last desideratum in syste- 

 matic botany ; and he early attempted to collocate most known 

 genera under natural orders (e. g. Piperitce, Palmce, Scitamince, 

 Orchidea, Amentacece, &c., sixty-seven in number, including his 

 four cryptogamic orders) , but without definition or arrangement. 

 In his later years, he was unable to accomplish any thing more. 

 The difficult problem was taken up by Linnseus's contemporary 

 and correspondent, Bernard de Jussieu, who planted the botanic 

 garden at Trianon with plants grouped into natural orders, but 

 published nothing. His pupil, Adanson, who when a young 

 man lived for several years in Senegal, and who was as remark- 

 able for eccentricity as for erudition and ability, published in 

 1763, in his Families des Plantes, the first complete system of 

 natural orders. But he seems to have taken little from his 

 teacher, and with all his genius to have contributed little to the 

 advancement of the natural system. 



689. Antoine Laurent de Jussieu, nephew of Bernard, has 

 been called the founder of the natural system of botany, and to 

 him more than to any other one person this honor may be 

 ascribed. In his Genera Plantarum secundum Ordines Natu- 



disposita, 1789, natural orders of plants, one hundred 



