244 de Fr aine. — The Morphology and Anatomy of the 
increased luxuriance is due in these cases largely to the mulch action of the 
advancing fan, which acts by retaining a damp zone around the growing 
points of the plants, enabling them to grow for a time with greater vigour. 
Eventually, it would appear that the rapid raising of the surface level pro- 
duced by still further additions of shingle proves disastrous for a plant 
whose only method of combating the attack is to increase the length of the 
petiole in the effort to bring the leaves well above the surface again. 
It would thus appear that the restriction of .S', binervosa to its very 
limited habitat depends entirely on the ill-equipment of its underground 
parts. It is unable to colonize mobile shingle, not because of the arid 
conditions and lack of humus, but because of its inability to rejuvenate 
when covered, and because, as will be seen later, the structure of the 
stem is unsuited to vigorous branching accompanied by rapid growth, and 
on the other hand it cannot compete with other colonizers of the crest of 
the stable laterals, since the centrifugal extension of the turf of the various 
grasses, or of rhizomatous plants, or of cushion plants subjugates it, hence it 
is practically restricted to the narrow belt of ‘ No Man’s Land ’ on the 
sloping flanks of the laterals, where the conditions are probably more 
rigorous in many respects than in any other part of the area, and where it 
reigns supreme. Here the water-supply is extremely limited on account of 
the slope, the food-supply is small, for the accumulation of humus is com- 
paratively slight, and exceptionally high tides may deposit a coating 
of mud over the plants ; as will be shown later, the anatomy of the plant is 
well fitted to enable it to endure all these adverse conditions. 
Statice beltidifolia (= reticulata ). 
This species invariably occurs in situations reached by all but the 
lower tides, and especially in the muddy shingle lows already described, 
which remain moist throughout the inter-tidal period. 
The conditions of life in these lows is thus very different from those on 
the sloping flanks of a lateral, and approximate at certain times to those of 
a salt marsh, where, too, the plant is sometimes to be found. After a very 
high tide the salt water stands in the lows, converting them into small 
lagoons from which the water escapes only very slowly by percolation ; s the 
tide is left in them long after the Pelvetia and Aster marshes become fully 
exposed again. If the tides are exceptionally high and evaporation low, 
they may not become empty between two successive tides. It is clear that 
after a period of such unusually high tide, the salt water will remain standing 
in the lows for some time, so that 5. beltidifolia will have to face concentra- 
tions of salt water, and will thus be exposed at more or less regular intervals 
1 My thanks are due to Dr. Sarah Baker, who kindly made these observations for me during 
a visit to Blakeney in November, 1913, in order to study the especially high November tides of 
that year. 
