504 ECOLOGICAL STUDY OF SALTMARSH VEGETATION. 



was invaded by this weed which took possession of a portion of 

 the lawn on the marsh front about an acre in extent. Its 

 optimum was reached in midsummer when hardly a blade of 

 grass could be seen in its carpet, but when again visited in 

 midwinter not a vestige of the Soliva was visible and the Couch 

 dominated the recently invaded area. A congener, tioliva 

 anthemifolia K. Br., also of annual duration and with similar 

 foliage is less aggressive, rarely spreading over more than one 

 or two feet of turf during its period of activity. S. sessilis 

 succeeds best in a sandy soil and is tolerant of moderately dry 

 conditions, its congener displaying a preference for a moist 

 clayey alluvium, neither advancing into the brackish station on 

 the margin of the salt-plain. S. sessilis was first recorded for 

 Australia by Maiden and Betche* and was figured and described 

 by Maiden f. It is not known when S. anthemifolia appeared in 

 Australia, but it is viewed as a doubtful member of the native 

 vegetation. Both species are indigenous in South America. 

 The distribution of the seeds of S. sessilis is probably carried 

 out by animals, the pointed dart at the apex of the achenes 

 piercing their skins, or the marginal irregularities becoming en- 

 tangled in their coats. The achenes of S. anthemifolia emit 

 mucus when wet and would adhere to the plumage of birds. In 

 both species the achenes have but a few hours' flotation. 



Two Buttercups, Ranunculus muricatus L., a tufted annual 

 introduced from the Mediterranean region, and R. rivularis Bks. 

 and Sol., a stoloniferous perennial, a native of Australia which 

 extends to New Zealand, meet in the boundary pasture. Both 

 species find a limiting factor in this station, insufficient moisture 

 retarding the progress irdand of R. rivularis — normally an 

 aquatic, with finely dissected leaves — which reaches its highest 

 stage of development when submerged. R. muricatus is pre- 

 cluded from advancing towards the salt plain by the salinity of 

 the station. The latter clears a space for its tufts by spreading 

 its stiff basal leaves in the form of a rosette and overlying the 

 grass in its vicinity. Its associate, on the contrary, is pressed 

 by the stouter herbage into an upright growth, its weak foliage 

 reclining on the sward. Large colonies of R. rivularis occur 

 in the muddy flats on the banks of Cook's River, R. muricatus, 

 in its season, spreading over the inland Couch sward. The 



* These Proceedings, xxiv., 1899, p. 646. 

 tAgric. Gazette N.S.W., 1917, p. 183. 



