PRESIDENTIAL ADDRESS. 
179 
branch in order to rid itself of a nuisance, does not seem to be 
capable of proof, although it is popularly believed to be the means 
of dispersal. 
Whichever derivation is chosen, it is by means of birds that 
the seeds are deposited on neighbouring trees, and, in most 
instances, perish for want of suitable conditions. A stray seed 
here and there, however, lodges in some crack on the bark or 
in the roughened coats where a branch is given off, and remain- 
ing there in security is able later to force its roots into the next 
layer of soft wood below. It thus soon reaches a good supply 
of food, because this layer immediately below the bark is specially 
full of sap, being the one by which the tree makes active growth 
each year. Once having started to grow the little roots or pegs 
increase in length until they find the firm woody tissue of the 
branch, and there they cease to penetrate. The pegs possess 
the power to elongate themselves at their base instead of at the 
tip, and in that unexpected way add to their length. It is the 
host which grows thicker each year, and as it increases it 
envelopes the pegs upwards, so that they become surrounded more 
deeply by woody tissue and are firmly fixed. Meanwhile the 
Mistletoe gives off new rootlets immediately under the bark, and 
these in their turn send out fresh pegs to penetrate to the hard 
wood and to be enveloped in due time by the increased growth 
of the branch. By cutting open a branch carrying a well estab- 
lished bunch of Mistletoe, it will be seen that the root pegs are 
arranged in a row — they have been compared to the teeth 
of a garden rake, and they enter at the side of the branch. 
Having established its growth by rows of pegs within the tree, 
the visible portion of the Mistletoe plant outside the bark pro- 
ceeds in its turn to develop. It may be years before it makes 
much promise of a bush, according to the amount of food which 
its host is able to provide. As it increases its bark becomes of a 
light green colour, and its leathery leaves also take on a greenish 
tint, both caused by the presence of the green chlorophyll within 
the cells. This chlorophyll helps to make a supply of food, just 
as it does on a much larger scale in the green leaves of other 
plants, so that the Mistletoe is not entirely dependent on the 
sap of the tree for all its food. 
It is on account of this partial supply that the Mistletoe is not, 
after all, the worst form of parasite, like the dodder or broomrape 
that have no green leaves, but it still remains to be considered 
botanically a degenerate plant. 
The Mistletoe originally produced all its own food, but having 
acquired the habit of getting free meals from a liberal host, it 
has gone a long way towards losing its independence, and only 
helps itself by forming a limited amount of chlorophyll in its 
leaves. Such a downward course might be imagined in the ivy 
and the Virginian creeper, where we have examples of plants 
that send forth rootlets by means of which they cling to walls 
or trees. They obtain no food from them, yet it would be easy 
