128 DR. J. W. HRSLOP HARRISON ON 



that the individual members were descended directly from one 

 and the same ancestor. Furthermore, it gave us evidence 

 that the purple green variety is heterozygous for colour and 

 therefore a hybrid (in the Meiidelian sense) between the red 

 and the green forms. 



In general, the species responsible for such primary 

 colonisation is Salicornia herbacea, but one tremendous colony 

 on a mud spit jutting into the Creek was solely composed of 

 S. dolichostachys. 



Very rarely, instead of Salicornia being the pioneer, 

 Glyce?'ia maritima appears in that role with marked success, 

 although never on a large scale. 



Sometimes succeeding Salicornia in the first phase, but 

 often enough occurring simultaneously, Suaeda ?naritima forms 

 an edging. Next, Glyceria maritima insinuates itself, until at 

 length the open Salicornietum passes typically into the 

 Glyceria-Salicornia association including nothing but the two 

 dominant plants and a little Siiaeda, although other segregates 

 of Salicornia europaea like S. disarticiilata and S. ramosissima 

 may occur locally. 



In the next evolutionary step the annuals practically 

 vanish, and an almost pure growth of Glyceria forms the turf 

 which, at the point where favourable conditions assisted the 

 present observations, gradually merges into an Armerietum, 

 a steady rise up the crumbling slopes leading us directly into 

 that part of the marsh which must have persisted for ages 

 and preserved this association in its stablest form. This 

 includes: — 



Armeria maritima d Plantago maritima f 



Glyceria maritima d Glaux maritima r 



Aster tripolium ... r 'I'liglochin maritinium r 



Artemisia maritima ... {on edge) r Festuca rui)ra o 



Whilst the above represents the distribution, and in part the 

 succession, in the west, to the eastward, events, which 

 unfortunately can only be followed on a minor scale, pursue 

 a different course. In newly colonised muddy hollows, soon 



