Notes axd Comment. 149 



ascending the larger hill masses, but in the lowlands iL does not 

 tnateriallv affect the distribution of dominant trees, although 

 it iniluenccs certain sj^ecics of the ground vegetation. vSoil is 

 tlie greatest differentiating factor and influences the distribu- 

 tion of woodlands thror.gh differences in mineral content, and 

 humus-content". 



The same botanists have recently published other pa])ers. 

 Rankin describes, in The NafKniliy't, the " Peat Moors of Lons- 

 dale," with s] ccial reference to the lowland Moors, which arc 

 either littoral or lacustrine. '1 he former, located in the drainage 

 area around Morecambe Bav in north and west I{ngland, are a 

 distinct ] In siogra] hie feature, and their vegetation sIuavs 

 relaticmshi]) with the fens (f eastern I^ngland. "The hrst vege- 

 tation grew in silt r.nder water, and in time became swamj) 

 moor, to 1 e f( llowed later l)y heath moors; these phases being 

 traceable from existing \ egetation and also from examination 

 of remains in the peat, the lowest strata consisting of sedges 

 and rushes, not lurch, as in the case of mcst upland peat moors." 



Moss, in llic New Phytoloqist, discusses "The Fudamental 

 Units of ^'egetati( n," tracing the liistorical development of the 

 concepts of the ])lant association and the plant fc.rniation fnun 

 Humboldt and Criesebach down to the works of living writers. 

 Warming's definition, "an association is a communitx of definite 

 floristic com] ( sition within a formation"' ma\ be comjared 

 with tliat of .M( ss, "A plant formatic n comprises the ]>n gressive 

 associations which culn.inate in one or more stai)le or chief 

 asscciatic ns, and the ietrcgressi\ e asscciatic ns which result 

 from tlie deca\ of the chief ass( ciati: ns, so k ng as tliese changes 

 cccui ( n the same habitat." 



Aside from the writers cited, all of whom ha\ e at least foruni- 

 latcd a problem of scientific interest and imj^ortance, toward 

 rhe solutifu oi which their wcrk has c( ntributed, there are 

 ( thers who have for the ni< st ] art limited themselves to record- 

 ing certain facts of distribution, which, like the lists ff species 

 given in s' stenatic j^eriodicals, are likeh enough at some future 

 time to ha\e more \ alue than is aj^j arent at present. On the 

 whole, howe\ er. it is j Iain that if to the recent work of European 

 botanists there is added that of American investigation in the 

 field of ph} togeography, there is reason to feel that notw itlistand- 



