506 ECOLOGICAL STUDY OF SALTMARSH VEGETATION. 



fruiting at a height of 1 to a few inches (Plate xxviii., fig. 24) . 

 Polycarpon tetraphyllum Loefl., a diminutive mat-forming eos- 

 moijolitan annual, common in sandy maritime stations, can only 

 maintain a position in the sward of a resting species or on a 

 vacant space, its weak growth offering no resistance to the 

 pressure of its stronger associates. On a newly reclaimed area 

 at Cook's River it was the only vegetation present, dotting the 

 ground with isolated mats some of which extended to 1 foot 

 in diameter. The persistent bracts and sepals of the closely- 

 packed flowers, which turn red in fruit, presented a striking con- 

 trast to the pale rain-leached sand. 



The Petty Spurge, Euphorbia peplus L., an introduced annual 

 with an upright habit, is forced into a rank growth by the damp 

 shady conditions obtaining in the lax pasture of the Casuarina 

 forest, its weak lanky stems supported by the surrounding herbs. 

 In common with many of its congeners, the Spurge secretes a 

 milky latex. The Pimpernel, Anagalis arvensis L., another cos- 

 mopolitan shade and moisture loving annual, with a decumbent 

 growth, also frequents the Casuarina forest, both the blue and 

 scarlet flowered varieties trailing succulent stems through the pas- 

 ture. Fimbristylis dipliylla Vahl., a tufted perennial sedge com- 

 mon in most warm regions, is occasional in the pasture where it is 

 non-competitive, its flaccid basal leaves folding vertically round 

 the stem when pressed by the grasses which it intrudes. Cheno- 

 poclium album L., the White Goose-foot of Britain, an adaptable 

 weed with a cosmopolitan range, enters most of the formations 

 from the boundary of the salt plain inland. Its lengthy taproot 

 penetrates the marsh mud undeterred by either acidity or salinity, 

 and can develop an equally vigorous growth in a comparatively 

 dry station if the soil is permeable. The plants maintain their 

 positions in the formations which they intrude, by building a 

 tall, spreading, leafy screen which acts as a deterrent to ap- 

 proaching competitors. Seeds of Chenopodium spp. were fre- 

 quently identified in the stomach contents of Australian birds 

 (38). 



The slopes on the boundary of the marsh are usually clothed 

 with a Couch lawn which is intruded by numerous ruderals, 

 chiefly Clovers, Medicks, Grasses and Thistles. The Clovers, 

 Trifolium spp. and Medicks, Medicago spp., are chiefly creeping 

 or procumbent herbs and make their maximum growth in the 

 moist meadow at the base of the slope, gradually weakening as 



