University of California Publications in Botany [Vol. 10 



INTRODUCTION 



The genus Fncus, although among the earliest established genera 

 of algae, having been studied on the Atlantic and Arctic coasts of 

 Europe by most of the algologists since the days of Linnaeus, is, 

 nevertheless, even today, a genus in which the limits of the species, 

 not only in European waters but also in those of Asia and America, 

 have not been clearly defined. The flattened, more or less flabellate 

 and mostly diehotomously branched fronds, together with the very 

 constant character of the formation of eight viable eggs in oogonia 

 borne in cavities in the modified ends of the fronds, quite definitely 

 delimit the genus from all other genera of algae ; but the discovery of 

 single characters, or combinations of characters, sufficiently stable to 

 serve in delimiting the multitude of species and forms has been a 

 matter much more difficult of attainment. About twenty-five species 

 and over forty varieties and forms have been previously proposed. 

 From time to time species have been reduced to varieties and to forms, 

 and these have in turn been raised to the rank of species, and the 

 species have been interchanged, according to the conceptions of the 

 different investigators of the group. This has gone on with increasing 

 complexity and there seems never to have been a time when more con- 

 fusion existed in regard to the disposition of the Fucus flora, par- 

 ticularly that of the Atlantic and of the Arctic waters, than the present. 

 The confusion is due to a variety of causes. One of the chief difficulties 

 one encounters in trying to get an understanding of the conceptions 

 of the early writers concerning certain species is the incompleteness 

 of the descriptions, adequate at the time to distinguish fairly well 

 the few forms then known, but wholly inadequate to serve in the 

 separation of species as limited by present day usage. Coupled with 

 the brevity of the descriptions, one often encounters an added difficulty 

 in the nature of poorly prepared, and for the most part, fragmentary 

 specimens preserved as types, if indeed any at all have been preserved. 

 I have quoted some of these early descriptions under proper headings, 

 and have also presented illustrations of some of the few type specimens, 

 which will serve, in some degree, to show the existing state of affairs. 



Since the days of Linnaeus our conceptions of species have been 

 and still are changing. Formerly larger units were grouped under a 

 single concept, and a few words were sufficient to embody the concept. 

 The general tendency has been to break up the larger units, assigning 



