BY A. A. HAMILTON. 501 



to this grass, together with valuable economic notes. Various 

 common names have been given to this species but the var. 

 nvrmule is perhaps best known as Water-Couch, and the var. 

 littorale as Sea-side Millet. During its active growing stage — 

 it is an sstival grass — it banks up a mass of divaricately- 

 branched herbage which overruns the intrusive annuals that 

 have taken advantage of its resting period to enter its sward. 

 The supremacy of the Paspalum in the brackish pools is fre- 

 quently disputed by J uncus prismatocarpus R- Br., a perennial 

 rush which adopts a similar arrangement of its colony. The 

 formations of the grass and rush are evenly matched in height, 

 density of formation, and mechanical structure, their respective 

 rhizomes, which feed on the same plane, maintaining the equality 

 of their competitive equipment. When colonising a new habitat, 

 which may have arisen through a favourable alteration in the 

 depth of water — the shallowing of a deep pool, or the Hooding 

 of a dry station — primary possession determines their relative 

 boundaries. Their joint occurrence in a pool is most frequent 

 in the zone between the fresh and brackish waters, the Juncus 

 exhibiting a greater partiality for salinity than its associate, 

 though equally capable of forming a sward in fresh water. 



The Mat-grass, Botbellia cornpressa L. f., an Asiatic species 

 which has spread along the coast of Australia and reached Tas- 

 mania, is a decumbent perennial with weak culms, which elongate 

 and assume a straggling habit when growing among rushes or 

 the taller Cyperaceous plants. Normally a swamp-dweller, the 

 Mat-grass can adapt itself to comparatively dry conditions and 

 is not averse to a degree of salinity. At Buffalo Creek (Lane 

 Cove), a vigorous growth of this grass has ranged behind a band 

 of Cladium junceum on the border of the marsh. In this station 

 it is able to maintain the integrity of its formation, but in a 

 dry habitat its density is broken and intruded by the Common 

 Couch and other lawn grasses. 



Two flaccid perennial Sedges, Seirpm inundatus Poir., and a 

 close relation, S. prolifer Rottb., occasionally join forces in the 

 invasion of a shallow pool in the fluvial station, their- weak 

 stems mingled in a ramifying growth. They are preferably 

 freshwater plants and do not proceed far into the brackish zone. 

 S. prolifer frequently produces a proliferous growth on the tips 

 of its stems — simulating vivipary — which l'oots when it reaches 

 the ground, affording the plants some assistance in the exten- 



