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THE PHYSIOLOGICAL ANATOMY OF THE 
VASCULAR PLANTS CHARACTERISTIC OF PEAT. 
J. H. PRIESTLEY AND MILDRED HINCHLIFF. 
The characteristic appearance of a peat moor must be familiar 
to any observer of Yorkshire vegetation. Whether the area 
be dominated by Calluna or Erica, by Eriophorum or Juncus, 
the character of the plants remains the same ; of stunted 
growth, dark green in colour, and of very leathery texture, 
with small leaf surface. More detailed examination reveals 
the leaves frequently inrolled, with sunken stomata and a 
thick cuticle ; and such characters have led inevitably to 
the peat plants being grouped with xerophytic plants. 
In botanical thought, dominated by the Darwinian point 
of view of natural selection, the attempt is usually made to 
explain form and structure in terms of fitness to surroundings, 
but in interpreting along these lines the peat plants, which 
occupy some of the wettest areas of the countryside, the 
ecologist is faced with a different problem. He has to explain 
why xerophytic structure is specially suited to such a wet 
habitat. The solution usually offered is that the water of 
the peat moor, though present in large quantity, is not avail- 
able to the plant owing to its acidity. So far as we are aware, 
however, this argument has received little support from 
experiment. 
The teleological point of view then in this case leads to 
difficulties not yet solved. It is therefore of interest to 
consider other lines of investigation, and in the present paper 
attention is drawn to certain other anatomical features 
characteristic of peat plants that have never yet been re- 
corded, as far as the writers are aware, whilst a reason for 
their presence is suggested, which does not involve a teleo- 
logical interpretation. It may happen that the facts here 
considered may throw some light on the characteristic features 
of the form and anatomy already noted. 
It has been stated already that an abnormally thick 
cuticle is a very constant feature of these plants. The cuticle 
of a plant consists very largely of cut in, a substance derived 
from various organic acids, mainly oxyfatty acids, which 
seem to occur partly condensed into complex molecules, 
partly as esters of the alcohols glycerol, phytosterol, and other 
higher alcohols (Priestley — 2). 
The rapid deposit of cutin on the young vascular plant of 
the peat moor suggests the presence of an abnormal amount 
of fatty acid. Anatomical investigation with the employment 
of micro-chemical methods confirms this assumption. Thus 
in Empetrum, Calluna, and indeed in practically every 
1922 Aug.-Sept. 
