478 ECOLOGICAL STUDY OF SALTMARSH VEGETATION. 



when eaten by birds. The small seeds, which are freed from 

 the capsule (dehiscent) when ripe, sink almost immediately when 

 immersed in water. 



Selliera radicans, another perennial carpet-forming species, is 

 occasionally present in the tide-flooded zone, the largest local 

 formation noted extending along the marsh margin at Iron 

 Cove. This formation stretches for a considerable distance in 

 a broad band, occasionally interrupted by unfavourable edaphic 

 intrusions. On the saline mud at the base of the \ marsh bank 

 its heavy succulent leaves are closely appressed to the ground, 

 overlapping in several layers, the resultant carpet presenting a 

 dense barrier to encroachment by the surrounding herbage. On 

 the landward boundary, the Selliera has attempted the ascent 

 of the sloping bank, but the Salt-grass, Sporobolus virginicus 

 Humb. & Kunth., which is firmly established in this station, has 

 obstructed its passage, its strong, wiry framework forcing the 

 soft fleshy stems of the Selliera to rise obliquely from the 

 ground. When the stems of the Selliera lose their grip on the 

 surface they trail over the Saltgrass sward, and as they are un- 

 able to again descend to root their further progress is arrested. 

 On the muddy flat the struggle for existence in the Selliera 

 carpet is very severe and has resulted in the production of short 

 crass leaves, sessile and crowded. The harsh conditions are also 

 responsible for a prolific growth of flowers, which are closely 

 appressed to the stems and almost cover the surface of this sec- 

 tion of the carpet. The flaccid aerial stems trailing over the 

 salt-grass are not subject to this competition and have responded 

 by the adoption of a lax growth habit, broadening the leaf 

 blades and raising them on stalks, reducing their turgid succul- 

 ence, and spacing them distantly along the branches (Plate xxix. 

 flg. 25) . A further response to the removal of the stress of 

 competition is the cessation of sexual reproduction, the well- 

 favoured stems either declining to produce flowers or reducing 

 the output to a negligible quantity. In the muddy station the 

 Selliera meets outlying tufts, or occasional patches, of Juncus 

 maritimus var., and surrounds them, closely investing the spaces 

 between the tufts. The association of Selliera and Juncus is 

 noted by Guppy (13) among coast plants in Southern Chile. 



The fruit, which is slightly succulent, retains the seeds when 

 it falls (indehiscent), but its weakly constructed walls are 

 readily permeable and soon collapse in water, releasing the seeds. 



