PRESIDENTIAL ADDRESS. 
181 
it is distinctly common on some of the species, notably on a grove 
of sycamores, on three long avenues of limes, and on several 
scattered acacias, maples, and hawthorns. One or two of the 
clusters are so uniform in shape that they look like a chandelier 
of green hanging from a slender bough, and can readily be seen 
by the most casual observer. On the white beam it is confined 
to one bush in Brockley Combe as far as is observed, and it is 
admittedly regarded as very rare on that host. When the plant 
is found thus plentifully distributed over a limited area and is 
comparatively rare elsewhere, the interest in its growth is much 
increased, and comparison is thought of with other counties where 
it flourishes. 
On the Gloucestershire side of the city it is scarce except on 
the apple and poplar, but we find it established on two additional 
trees, the grey poplar at Brentry, and a species of sugar maple 
planted in Tortworth Park, as well as on a few hawthorns, in- 
cluding a small plant on Durdham Down. Further observations, 
however, are needed for the county, and I commend the work to 
the notice of the members. 
Herefordshire stands out pre-eminentlv as the home of the 
Mistletoe in England, and the few species of trees on which we 
find it locally compare poorly with the 32 different kinds which 
have been observed by botanists throughout the county. With 
so many orchards there the number of Mistletoe berries distri- 
buted each year must be very great, but the explanation of its 
frequency on so many different trees must be chiefly due to some 
unknown conditions favourable to the plant, which must exist 
in a more limited extent in Somerset and only within such a 
small district as the Nailsea valley. 
The 32 different trees in Herefordshire consist of a number of 
species, many of them cultivated or foreign, but confined to a 
few Natural Orders, so the same law seems to apply, that it is 
only trees with special tissues which can act as hosts to this 
strange parasite. Just as with us the Mistletoe cannot be found 
on some of our commonest native trees, so in that county it does 
not grow on the beech, the silver birch, the hornbeam, the sweet 
chestnut, the holly, the blackthorn, or the elder, and, taking all 
the conditions into consideration, we may feel gratified with the 
display that is made close around Bristol. 
From the flora of Glamorgan we gather that the parasite is 
very rare in that county, and it is stated on good authority that 
not more than half a dozen solitary clumps have been noted 
throughout the whole of Glamorganshire, and no satisfactory ex- 
planation is forthcoming for this curious limitation of the plant. 
Apple trees and poplars, at all events, are plentiful there, and 
yet for some peculiar reason Nature refuses to permit the 
parasite to gain a footing on them. 
On broad lines of distribution, it is known that the chemical 
composition of the soil greatly influences the kind of plants that 
