best classifications given by special 'writers, there being no recent, single 

 work which gives a full account of the orders in all departments. 



The Filices, or Ferns, are arranged to suit Hooker and Baker's " Syn- 

 opsis Filicum, 2d ed., London, 1874." 



The Musci are made to conform to Schimper's " Synopsis Muscoram 

 Europseorum, 2d ed., Stuttgartiae, 1876." But the tables of the Musci 

 and the Hepatic* are taken, in great part, from Debat's "Flore des 

 Muscine'es, Lyon, 1874." That of the Musci, however, has been 

 revised, condensed, and modified to make it accord with the new edition 

 of Schimper's great work, Debat having used the first edition. The 

 orders Drepanophyllaceae, Phyllogoniacese, Hypopterygiaceae, including 

 mosses found only between the tropics or in southern latitudes, art- 

 inserted from Miiller's " Synopsis Muscorum, frondosorum omnium hue- 

 usque cognitorum, Berlin, 1849." 



The fresh water Algae are classified according to Rabenhorst's ''Flora 

 Algarum Aquae Dulcis et Submarine, Lipsiae, 1864-8." The marine 

 Algae are taken from Agardh's " Species et Ordines Algarum, Lundaj, 

 1848 76." 



Leading authors differ much in the systematic arrangement of the 

 Lichens, and a table cannot be made to suit more than one of the stand- 

 ard works. It was thought best to follow the latest, Tuckerman's "Gen- 

 era Lichenum, Amherst, 1872." The Fungi are given partly in accord- 

 ance with Cooke's "Handbook of British Fungi, London, 1871," as well 

 as his "Fungi; their Nature and Uses, New York, 1875," though 

 neither of these works is in full accordance with the present development 

 of mycology. 



The study of the genera and species of the cryptogamous plants is 

 difficult, because some of the parts on which the distinctions are based 

 are very minute, and require the use of the microscope; because the 

 range of variation in the same species is often large ; and because in 

 many of them the organs of reproduction are rarely met with. The 

 natural difficulties are still farther aggravated by the unnecessary multi- 

 plication of terms used by different specialists to designate similar organs. 

 Indeed, the almost limitless resources of the Greek language have been 

 severely taxed to supply words for successive authors, and there is, as 

 yet, no single glossary to be found which gives a full explanation of all 

 the necessary and the superfluous names. Another trouble yet is the 

 want of books describing, in one work, the whole cryptogamic flora of 

 one country. 



