L. Cockayne akd Foweraker. — Plant Associations at Cass. 177 



especially the' species of Raoidia and to the moss Racromitrium lanuginosum. 

 These Raoulias, according to the species, either collect more or less sand and 

 silt between their branches or the dead parts remain as peat within the 

 cushion. In any case, a seed-bed suitable for the well-being of various species 

 of other plants is provided, which, as they develop, in no few instances 

 kill their host, whose remains, however, add humus to the soil. Raoulia 

 tenuicaulis early on is thus suppressed. The following, in addition to most 

 of the species already noted, are important members of this stage of river- 

 bed : Carmichaelia Monroi, forming open semi-cushions of short, rigid, 

 flat, leafless stems ; the introduced Trifolivm arvense ; Raoulia lutescens, 

 forming dense, low, flat, silvery cushions in great profusion ; and the grey, 

 half-dead-looking HeUchrysum depressuni, a low shrub with minute appressed 

 scale-like leaves. The rare herb Myosotis uniflora occurs here and there; 

 it forms small moss-like cushions (see Plate XVI), and produces rather 

 large pale-yellow flowers. As the humus-content of the soil increases, 

 tussocks of Festuca novae-zealandiae enter into the association, and by 

 degrees low tussock grassland is established.* 



(C.) LIST OF SPECIES BELONGING TO THE ASSOCIATIONS DEALT WITH 



IN THIS PAPER. 



(Unless the contrary be stated, the species are evergreen. Introduced species marked 



with an asterisk.) 



* This is a very brief account of a most interesting series of associations, but a much 

 more detailed description is in course of publication by Foweraker. In the meantime 

 those who desire further particulars may consult L. Cockayne's paper, " On the 

 Peopling by Plants of the Subalpine River-bed of the Rakaia, Southern Alps of New 

 Zealand" (Trans. Bot. Soc. Edin.. vol. 24 (1911), p. 104), where the ecological con- 

 ditions of river-bed are discussed, a synopsis of growth-forms furnished, and the 

 ecology of the RaouUa-iorm dealt with. 



