30 Spartina Problem* 



close together Zostera is annihilated, the principal representative of the 

 associated ground vegetation being a small form of the alga Entero- 

 morpha. The higher levels of the flats are the first to be colonised. At 

 first single isolated plants appear, presumed to be seedlings; each plant 

 spreads laterally by means of stolons to form a circular or oval patch; 

 the rate of growth in any direction being from 2-3 ft. per annum under 

 favourable conditions. In this way the expanding tufts soon unite into 

 strips with open passages between — like a jigsaw puzzle approaching 

 completion — and finally meadow into practically continuous stretches 

 covering acres of mud (cf. PI. II, fig. 2). 



In their earlier stages the height of the grass shoots is uniform over 

 the patches, but as they expand (e.g. at 5-6 ft. diameter) the patches 

 become saucer-shaped owing to the haulms of the central, older parts 

 falling short of those at the periphery 1 . With the further extension of 

 the patches this marginal effect, though still persisting, becomes less 

 noticeable. 



The height reached by the grass in its growth varies from season to 

 season, depending particularly on the rainfall in the earlier part of the 

 summer. In this respect Spartina resembles Salicornia and the other 

 halophytes of the salt marsh. Flowering is spread over a long period 

 (July-November) with maximum in September. It is stated to be a 

 shy seeder in most seasons, with occasional bumper years. 



Spartina roots very freely from its underground stems. There are 

 two types of root: (1) long, anchoring roots which descend unbranched 

 in the mud for 2 or even 3 ft. ; (2) short, branched, superficial feeding 

 roots, so closely crowded together as to form a continuous plexus in the 

 surface layer (cf. Fig. 3; the sketch is reduced to \ nat. size). 



A marked effect of Spartina is the collection and holding of sus- 

 pended mud. The rise in level from this cause will sometimes reach as 

 much as 4 or 5 inches in a year, though it is not implied that this rate 

 of accretion is maintained indefinitely. The presence of the plant has 

 a marked stabilising effect on the mud, so much so that it is possible 

 to walk about on the meadows in relative safety. 



Except where the Spartina meadows approach the shore they form 

 pure stands, free from invasion by other halophytes. It seems too early 

 to say whether Spartina is destined ultimately to give place to other 

 vegetation, though judging from analogous cases such replacement may 

 be regarded as probable. Should such a succession occur there is no 



1 At the present time this "marginal effect" is well shown by numerous patches of 

 Spartina in Holes Bay bordering the L.&S.W. Railway to the west of Poole Station. 



