BY A. A. HAMILTON. 483 



very similar in structure and habit of growth to its associate — 

 both have the convolute leaves of the xerophyte, and a spike-like 

 inflorescence — and their boundaries, though usually very decided, 

 are not readily discernible, especially when they are not in flower, 

 the height of the Sporobolus sward where the formations meet 

 approximating that of the Zoysia and accentuating the homo- 

 plasy. The two grasses are frequently associated both in the 

 saltmarsh and on the seashore, occupying relatively similar posi- 

 tions in either station, the Zoysia forming the larger colony on 

 the dune and the Sporobolus dominant in the marsh. 



In their coastal traverse the Zoysia is frequently found in- 

 truding a lawn of Common Couch, Cynodon dactylon Rich., 

 several miles inland, but the Sporobolus rarely leaves the vicinity 

 of tidal waters. The Zoysia ranges from the maritime sands of 

 Eastern Asia to New Zealand, where according to Cheeseman* it 

 ascends to 2000ft. at Lake Taupo and in Canterbury and Otago. 

 The Sporobolus, which is common in saltmarshes in the interior, 

 reaches its optimum growth in the local marshes on the infre- 

 quently tide-flooded plain, slightly uplifted, and with a fresh 

 water seepage reducing the soil salinity (Plate xix., fig. 5) . The 

 small, hard, mature grains of the Sporobolus are naked when 

 ejected from the glumes and hang for some time on the outside 

 of the spikelets before falling. 



2. The Dry Salt Plain. 

 The stretch of dry salt plain extending from the tide-flooded 

 area to the fluvial zone is for the greater part bare, the detritus 

 heaps and ridges usually formed round the decaying stumps and 

 roots of the dead Mangroves or other obstructions, and the pools, 

 channels, and moist depressions, harbouring a few hardy pion- 

 eers, chiefly fugitives from the adjoining formations, which 

 eventually prepare the habitat for the advent of the fluvial vege- 

 tation. The detritus heaps are frequently coated with a sward 

 of Sporobolus virginicus and outlined with an edging of Sali- 

 cornia, the latter seated on the plain (Plate xx., fig. 8) . The 

 severity of the conditions prevailing in this station is exemplified 

 by the efforts of the Sporobolus to invade the salt plain. An 

 outlying stem from the sward creeps down the side of the mound 

 and pushes out on to the bare plain. Flattened and closely ap- 

 pressed to the surface, it proceeds for a short distance when its 



* Manual Fl. N-Z., p. 844. 



