Reaction and Succession in Relation to the Plant Covering. 4 1 9 
being more or less intermediate (organic 2-74 per cent., carb. 093 percent.). 
The chloride estimations show that the percentage of these may become 
very high (6-3 4 per cent.) in the Salic ornietum , doubtless, as also in the case 
of the 3* 5 per cent, recorded for the large how on the Long Hills, an out- 
come of evaporation. 
The estimations for the Suaeda zone on the lateral beaches show that 
it flourishes in soil with as high an organic content and with a carbonate 
content as high as the average for the • Salicornietum. Similarly, the 
appended values for an old Obione marsh on the marrams area obtained by 
Mr. Hanley indicate that the proportion of organic material is not the 
determining factor for this species. 
Old Obione marsh marram 0-4 Organic matter 12.64 Chlorides 0-684 
}} >> 4-10 ,, ,, 7*59 >> °" 57 ^ 
>> ' 10-14 „ „ 3*20 „ 0.342 
The observed gradient, then, with respect to carbonates and organic 
material, when we pass from the Salicornietum to the Suaeda zone on the 
Pelvetia marsh would appear to be important as an indication of the 
varying conditions rather than of significance in itself. 
The differences observed are indications of the change in level and the 
consequent change in frequency and degree of their tidal inundation. 
That neither Obione portulacoides nor Suaeda fruticosa is tolerant of very 
high salinities is shown by their normal method of occurrence and growth 
behaviour. The former on old saltings is especially characteristic of the 
high banks of the creeks and hummocks, whilst the latter not only attains its 
maximum luxuriance in the upper part of the Suaeda zone, but, by the high 
development of anthocyanin pigmentation which it frequently exhibits in 
the low-lying areas of its distribution, betrays the existence of conditions 
which, whilst favourable to the formation of assimilates, are unfavourable to 
growth — conditions, that is, of physiological drought. 
As noted by Professor Oliver at Erquy in Brittany, halophytes are 
very susceptible to the influence of rainfall (New Phyt., vol. v, p. 190, 1906), 
so much so, that the extent of growth made would appear to be largely 
conditioned by whether the precipitation for any given season falls mainly 
in the periods of the ‘ neap 5 tides or the ‘ springs ’. This would seem 
to show that growth remains more or less in abeyance except during the 
periods following rain when the soil solution is relatively dilute. The 
appended data obtained at Erquy not only illustrate the rapid effect of 
rain in leaching out the chlorides, but also how much this is accentuated by 
the slightly higher level in the region occupied by the Glyceria sward, and 
still more by the higher level of the raised bank occupied by Obione. 
(During the period of observation none of these zones were reached by the 
