PROCEEDINGS 
OF THE 
PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
SESSION 1880-81. 
November 18 th, 1880. 
James Geikie, Esq., LL.D., F.R.S., President, in the 
Chair. 
Dr Buchanan White exhibited the roots of a plant 
which had been found choking a large pipe which con¬ 
veys water to mills at Blairgowrie. The pipe is about 
seven miles long, and is formed of the usual tile-pipes, 
fastened at the joints with Portland cement. The 
roots are said not to be found in the reservoir, but as 
they clearly have not arisen inside the pipe, it was 
suggested that there must be some openings by which 
they could find their way into it from the outside. On 
enquiry it was found that there were several leakages 
in the pipe, and it is by them that the roots must have 
entered, and then increased to such an extent 'as to 
choke the pipe. What the species is it is difficult to say 
from the specimens sent, but it is possible that it is a 
species of Equisetum —a plant which has been found to 
cause similar annoyance in other pipes elsewhere. The 
remedy is, of course, to prevent its entry by taking care 
that the joints are properly filled with cement. 
It was intimated that Mr Charles MTntosh, Inver, 
had made a valuable donation of plants to the Museum. 
Dr Thom, jr., Crieff; Mr Chrystal, Perth Foundry; and 
Mr Henry Curr, Pitkellony, were proposed as new 
members. 
The following papers were read :— 
1 . “Is Poly podium flexile distinct from P. alpestre?” 
By Dr Buchanan White, F.L.S. 
The Mountain Polypody Fern ( Polypodium alpestre) 
is not uncommon on some of the higher mountains of 
Perthshire (such as Ben Lawers) above an altitude of 2000 
feet, and resembles very much in appearance the Lady 
Fern (Athyrium filix-fceminaJ for which it was long 
mistaken. In a barren state (that is when the plant 
is unprovided with these little collections of seed-cases 
situated on its under surface, and technically called 
sori) it is difficult to distinguish the Mountain Polypody 
from the Lady Fern, but when it is fruitful the differ¬ 
ence is easily recognised. The Small Mountain Poly¬ 
pody (Polypodium flexile) is not found within the 
boundaries of the county of Perth, but occurs within 
the district drained by the Tay and its tributary 
streams, namely, on Ben Aulder, to the north of Loch 
Rannoch. It is (or was) also found in Glen Prosen in 
Forfarshire, and is said to have been met with also in 
the north of Scotland. It has not been observed in any 
other country. The author exhibited specimens of 
both ferns, and read extracts from various handbooks 
of botany to show the difference of opinion regarding 
the question under discussion—namely, whether the 
two ferns are distinct species, or whether one is a 
variety of the other. From this it appeared that all 
modern authors regard flexile as a variety of alpestre 
except Professor Babington, who is also not quite so 
confident in affirming its distinctness as he once was. 
The points of distinction between the two forms was 
then pointed out, from which it appeared that the only 
constant marks of difference are the narrow base of the 
pinnules and somewhat narrower frond of flexile , in 
addition to its habit of carrying the fronds nearly 
parallel with the earth, instead of erect or sub-erect. 
Generally, however, the pinnae are deflexed, or point 
down the stem of the frond, instead of pointing straight 
out or upwards ; and the fruit is more abundant at the 
base of the frond, and disappears towards the apex. 
