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PRESIDENTIAL ADDRESS. 
to think that in some species these rootlets, under favourable 
conditions, might start on a parasitic existence and adapt them- 
selves to drawing sap from their supporting trees, and so set up 
a scheme of feeding at another plant's expense. 
Other speculations arise in one's mind concerning the 
Mistletoe. When one looks at the different sorts of trees on 
which it grows, and we know from observation that it flourishes 
successfully on each of them, we may wonder how it manages 
to assimilate the various kinds of sap that form its food. The 
property common to all the trees on which I have found it is 
their astringency, which is allied to tanning material, and that 
property in its turn is acquired by the bark of the Mistletoe. 
A learned authority states, however, that the ash of the plant 
shows quite a different chemical result from that of the host, 
so the Mistletoe must possess the ability to rearrange and make 
use of the saps for its own requirements, and be a skilled master 
in gathering the best from each kind of tree. The greenish 
flowers which appear in March are very inconspicuous, of two 
sexes, borne on separate plants. The golden pollen from one 
is carried by small flies to the sticky ovary of the other, which 
becoming fertilised produces the familiar berry. When the fruit 
is fully ripened it has turned from a light green to a whitish 
colour. This is not the dense white that is seen in the snow- 
berry or in flowers, caused by air in the cells, but a clear semi- 
transparent white, such as is found in the garden currant. The 
advantage of the colour to the Mistletoe lies in it causing the 
fruits to be conspicuous against the brown or grey background 
of the leafless branches, and, in this way, they are more easily 
seen by birds, so as to afford them food, and by their short flights 
to transfer the seeds to neighbouring trees. 
The general distribution of a plant is often described by the 
botanist as " common," " local," or " rare," and on these lines 
the Mistletoe would be classed as " local," because, although 
it is fairly frequent on different trees in some places, in others it 
is rarely seen except in some old-established orchard. The wide 
and extensive Nailsea valley, from Bristol to Yatton, is a district 
where it grows abundantly, and it is in this portion of the Bristol 
coalfields that my observations have been chiefly made. There 
I have seen it without much difficulty in nearly every orchard, 
and on nine other species of trees, whereas elsewhere in 
Somerset it seems to be limited almost entirely to apple trees, 
with an occasional poplar or hawthorn. The trees that act as 
hosts in the Nailsea valley are the sycamore and maple ; the crab- 
apple, hawthorn, white beam, and pear ; the acacia, lime, and 
poplar. 
These trees belong to six different orders, which shows that 
the Mistletoe is able to make itself at home on trees that differ 
considerably in their characters. It must not be thought that 
on these trees it can be met with only here and there, because 
