1911-12.] BOTANICAL SOCIETY OF EDINBURGH 33 



as regards Algae the terminology clearly shows that the 

 concepts are different. 



It would appear that formation as used by Borgesen, 

 implies association as used by Warming. 



According to the former, the word formation is used to 

 denote a group of different species belonging, as in the 

 Fucaceae formation of a sheltered coast, to the same family ; 

 whereas, if one correctly interprets the latter, the word 

 formation is used to designate the entire group of Algae 

 (limno- or halo-nereid formation according to the fresh- 

 or salt-water habitat). 



Borgesen's association appears to be a formational unit 

 consisting of one species only, while Warming's association 

 seems to imply a group of plants of one, two, or more species 

 all growing together under the same or similar conditions : 

 or, in his own words, which must be taken to refer to ter- 

 restrial vegetation only, " an association is a community of 

 definite floristic composition within a formation " (p. 145). 



Thus it will be seen that while under certain circumstances 

 the idea of association as used by both writers is the same, 

 yet in the majority of cases formation, as used by Borgesen, 

 means association as used by Warming, and the association 

 of the former is the plant society of Moss (p. 48, 1910). 



The suggestion which the present paper wishes to em- 

 body is, that as ecological terminology is now fairly definite, 

 and accepted as such at least in Great Britain, an effort 

 should be made to use the same terms, if not to the entire 

 range of cryptogamic botany, at any rate to marine Algae. 



Just as a terrestrial formation may be divided into two 

 or more sub-formations, the nereid formation (of Algae) is 

 divided by Warming into two sub-formations : 



(a) Fresh-water (limno-nereid). 



(b) Marine (halo-nereid) (p. 169). 



It is customary to distinguish in the latter sub-formation 

 two regions : 



(a) the littoral ; (6) the sub-littoral. 



These regions could then be again divided into associa- 

 tions and plant societies, according to groups, single species, 

 or in many cases successive storeys, but it will be seen that 

 the sub-littoral habitat would be a great drawback in actual 

 delineation of group boundaries. 



TRAXS. BOT. SOC. ED1X. VOL. XXVI. O 



