INTEODUOTION. 



Devonian and Silurian systems. Throughout the 

 Tertiary, and in some of the Secondary series, remains 

 of Charophytes abound in the freshwater and estuarial 

 deposits. In the second volume we hope to give some 

 account of these. For the present it will suffice to say 

 that the fossil remains of these plants which have so 

 far been discovered do not throw any light on the 

 relationship of the group to any of the other divisions 

 of Cryptogams. 



The Charophyta are distributed almost 

 grap 1 a ^jj^Qughout the world, representatives 



of the group having been found from 

 69° north in Northern Norway to about 49° south in 

 Ker'guelen Island. The Warm Temperate Zone is 

 the most prolific as regards number of species, but they 

 are also very mimerous in the Cool Temperate Zone. 

 In the Tropics they are less numerous and within the 

 Arctic Circle there are very few. The Charophyte-flora 

 of many parts of the world has been so imperfectly 

 investigated that it is hardly safe to venture on any 

 generalisations as to the details of distribution. Braun 

 and Nordstedt's invaluable ' Fragmente einer Mono- 

 graphie der Characeen ' furnishes complete informa- 

 tion as to the known distribution of the various 

 species up to the time of its publication in 1882. 

 Since that date some additional localities representing 

 important extensions of distribution have been put on 

 record, and a large number of new species have been 

 described, but the latter clearly represent very unequal 

 values, and while some are evidently remarkably 

 ■distinct, only a small portion can perhaps at 

 present safely be ranked with the species in the 

 * Fragmente,' the claims of which to be regarded as 

 distinct have been passed by the two greatest authori- 



