82 BOTANICAL EXCURSIONS MADE BY 
Met Mr. Gorrie at the end of the woods and were conducted by 
him to Prestonhall Woods. Visited the gardens and house, 
where we were kindly received by Mr. Burn Callender. 
Saw a number of interesting specimens of roots which had 
entered into drains and caused their closure ; many plants seem 
to do so. One shown was the root of a walnut tree, which ha 
been traced by Mr. Gorrie 24 yards from the bole. Mr. Gorrie 
states that he has known it occur in the case of the elm, willow, 
poplar, and ash. A case of the latter kind I saw at Southampton ; 
it had occurred in drains in Hampshire. and was given to me by 
Mr. Balloch. Mr. Gorrie states that many herbaceous plants 
have roots which enter drains; among them may be noticed 
Polygonum Bistorta, Equisetum, Tussilago Farfara, which he has 
seen entering drains three feet deep. The bistort is particularly 
troublesome, and has caused much injury in the Carse of 
Gowrie. 
In Mr. Callender’s hothouse we saw a plant of Cereus grandi- 
florus with 9 or 10 flower buds expanding. We also tasted 
ripe coffee-berries and figs. Saw a mountain ash, one of the 
branches of which had been split off so as to leave the centre of 
the trunk bare ; the tree lived with the main shoot growing and 
numerous branches; from some of these roots were sent down 
which filled the split and broken portions of the bole. These 
roots were distinctly seen proceeding from the upper branches 
and forming a distinct covering to the exposed wood. The 
roots proceeded from the new wood near the bark of the branches. 
It is proof of the existence of a descending system, and is in 
favour of Gaudichaud’s theory. Saw an elm the main trunk of 
which had been broken ; a knot existed on the remaining part of 
the trunk, which gave offabranch. This branch now grows erect 
and has a peculiar bushy aspect, quite distinct from that of the 
elm, some of the branches of which in their natural state are 
seen. On all the branches of the new leader there is a tendency 
to develop knots, in fact the whole of them are covered with © 
knotty excrescences ; this peculiar tendency, as well as the habit 
of growth, continues in slips which Mr. Gorrie has taken from the 
plant. 
In the woods of Prestonhall the chief plants found were :-— 
