130 • DR. J. W. HESlOP HARRISON ON 



when the immense masses of Statice limonium flood the central 

 areas with their deep lavender blossoms in August and 

 September. 



On the north side the Arineria zone is succeeded by a narrow 

 band of Artemisia vulgaiis which locally yields to Obione 

 portulacoides, in the sole station for this very common saltmarsh 

 plant on the Tees. 



This thin line of Artemisia and Obione then is followed by 

 a mixed association compounded of common weeds of cultiva- 

 tion, plants typical of a littoral meadow, and similar plants. 

 Of these the most interesting are Bupleun/m tenuissimum, 

 Cochlearia officinalis, Agropynim juuceum and Stellaria 

 Boraeana. 



We must now turn our attention to the Secondary Marsh ; 

 this, we must remember, is simply a section of the fixed 

 Primary Marsh which by tidal wash has been thrown down a 

 foot or two below its former level. In consequence, it is now 

 subject to periodic immersions in salt water so that plants, 

 tolerant enough of salt in an ordinary way, but as we glean 

 from their stations in the upper marsh objecting to it when in 

 excess, now receive that excess. Practically immediately they 

 fail before altered conditions v^^hich Glyceria can withstand, 

 and that plant replaces them everywhere. In this fashion, a 

 close, if undulating, turf of what I call a retrogressional 

 Glycerietum is generated, often leading directly into the 

 Staticetum of the marsh above. 



This connection arises gradually as the new association 

 establishes itself and accumulates soil, thus raising itself once 

 again beyond the tidal influence. Then, and not till then, either 

 by " peaceful penetration " down the slope or by regeneration 

 from old roots, Statice forthwith proceeds to battle for its 

 position in the former joint dominancy. 



Greenabella Marsh. 



Like Saltholme Marsh, this has been shut off' by a sea wall, 

 but in this instance the barrier is the very massive double slag 

 wall retaining the lower half of Greatham Creek. In place 



