28 ON SYSTEMS AN D CLASSIF1 CATIONS, 



These defects and some others, from which no system can easily 

 be exempted, have suggested to several botanists the possibility of 

 correcting them and making the system more useful. Among ali 

 the improvements of the Linnaoan system, those by Thunberg, seem 

 to be the chief. He has reduced the number of classes to twenty, 

 by referring the plants of the 20th, 2 1st, 22d and 23d classes to 

 others, according to the number or connection of the stamens. 



All the plants which stand in the 20th class ought to have the 

 stamens placed upon the style ; but the most of the plants arranged 

 by Linnaeus in this class wants these characters, the genus of Orchis 

 alone excepted. The three following classes are not always con- 

 stant with regard to sex ; a difference of climate will sometimes 

 remove a plant from the crass Moncecia to that of Polygamia. 



Liljebad has made the following changes on the Linnaean system. 

 He joins the 7th, 8th and 9th classes to the 10th. His Decandria 

 thus contains the Heptandria, Octandria, Ennaeandria and Decan- 

 dria of Linnaeus. The eleventh -class he joins to flie 13th. The 

 18th, 21st, 22d, and 23d he includes in one. Thus his system con- 

 tains only sixteen classes, viz. 



1. Monandria, 9. Polyandria, 



2. Diandria, 10. Gynandria, 



3. Triandria, 11. Didynainia, 



4. Tetrandia, 12. Tetradynamia, 



5. Pentandria, 13. Monadelphia, 



6. Hexandria, 14. Diadelphia, 



7. Decandria, 15. Syngenesia, 



8. Icosandria, 16. Cryptogamia. 



Some other botanists have changed the orders of the 19th class, 

 by leaving out the word Polygamia, and removing the plants of 

 the order Monogamia to other classes. 



But this order of the 19th class ought to be altogether suppress, 

 ed ; because the genera belonging to it have nothing in common 

 with the other syngenesious flowers but the united anthers, which 

 other genera, for instance, the Solanum, possesses likewise. If this 

 order be taken away, the class becomes perfectly natural. 



Schreber, in the last edition of the Genera Plantarum, has chan- 

 ged the Orders of the 24th class, as follows : 



1. Miscellanaja. 4. Hepaticae. 



2. Filices. 5 Algae. 



3. Musci. 6. Fungi. 



