BY A. A. HAMILTON . 4(35 



Zonation. 



The zonal system in our marshes is largely regulated by the 

 edaphic conditions, in which soil salinity and the degree of sub- 

 mergence play a prominent part. The muddy, tide-Hooded area 

 on the marsh littoral, followed by a barren stretch of saltplain, 

 with its detritus heaps and shallow pools and channels, and the 

 marginal zone, with a reduced soil salinity consequent upon the 

 spread of the fluvial stream over the surface, each form distinc- 

 tive stations occupied by selective formations. The dominant 

 arboreal species, the Grey Mangrove and the Swamp Oak, oc- 

 cupy, respectively, the seaboard of the marsh and its landward 

 margin, herbaceous formations clothing more or less effectively 

 the intervening area. The curvature of the marsh on its lit- 

 toral front has necessitated the adoption of a semicircular, or 

 horseshoe-shaped, zonal arrangement by the various formations, 

 each in succession forming a border, more or less regular, on 

 its neighbour's boundary. The formations in the centre of the 

 marsh expand radially, those on the landward side narrowing 

 into elongated bands and extending bilaterally. The detrital 

 uplift of the landward bank and its forward movement on the 

 plain dislodge the marginal formations, either suppressing them, 

 or driving them towards the centre of the marsh, and replacing 

 them with the series next in the line of succession. 



The creeping, or carpet-forming, perennial herbs — grasses, etc., 

 — which constitute the major portion of the vegetation in the 

 marginal zone, are annually intruded by ephemeral ruderals, 

 which consummate their life-history during the resting period of 

 their hosts, the cycle closing contemporaneously with the arrival 

 of the season of activity of the permanent plants. Monocarpic 

 herbs of longer than annual growth also enter these formations, 

 their (usually) vertical roots operating in a sphere complement- 

 ary to those of the perennial rhizomatic species. 



Special Features. 

 The distinctive note in the saltmarsh proper is uniformity, 

 the vegetation covering large areas of our marshes maintaining 

 a strikingly symmetrical arrangement, the principal formations 

 displaying an even contour level and a decided zonal boundary, 

 though, in sections where the physical factors operate irregu- 

 larly, salients of greater or lesser depth are formed on their lines 

 of division, and the shapeless detritus heaps on the salt plain 

 are occupied by variform assemblages. The landscape of the 



