426 MR. G. C. DRUCE ON 
panicle and the early unopened one are present on the same 
individual. 
Some of the other specimens labelled P. lava should be placed 
under P. alpina rather than P. acutifolia, although in all cases the 
leaves are either gradually tapering or rather abruptly narrowed 
to a point, that is, are not conspicuously hooded. In the 
P. alpina sheet, consisting of A. Croall’s ‘ Plants of Braemar,’ 
no. 161, Lochnagar, Aug. 1854, two plants are inseparable from 
my acutifolia, but the centre specimen is a luxuriant and possibly 
cultivated specimen of P. alpina. 
“The Spout,” which has been referred to, is a narrow gully 
with an eastern exposure, by which one can with some difficulty 
ascend from the corrie near the Loch on the east side of Lochnagar 
to the summit of the mountain. I have visited this place three 
times at different seasons. The walls are of rather smooth rock, 
and are deep enough to give an amount of shade which can only 
be broken for a short time in the day, and that before the sun 
has much power. Although there is no permanent stream in the 
gully, there is considerable moisture, and there is always a move- 
ment of air up or down the rift, so that the predominating factors 
here are low temperature, nearly complete shade, nearly perma- 
nent moisture, and continual wind-currents: need we therefore 
be surprised that a grass like P. alpina, which has a considerable 
range of variability, should in such a situation produce some 
marked variation? The nearly complete shade, low temperature, 
and damp atmosphere necessarily lessen transpiration ; therefore 
the normal plane surface of a leaf would tend to remain unaltered, 
and the leaves elongating would become narrower and more 
pointed in shape, while in a dry exposed situation the tendency 
would be for the leaves to shut up or enroll. In passing one 
may refer to the broad and blunt, and the narrow and pointed, 
forms of the leaves of Poa pratensis. The same factors of shade, 
low temperature, and moisture act, as do short seasons, in lessen- 
ing the chance of the plant-cycle being completed in the year 
moisture being inimical to pollination, especially in anemopbilous 
species ; so that “ vivipary,”’ or rather the reproduction of the 
plants by bulbils, which is less dependent on warmth and light, 
is induced, and this condition once set up is readily perpetuated : 
so we see that Mr. Hanbury’s specimens remain in that condition, 
although removed to a lowland and more southern home ; and 
this is also true of Festuca ovina. In the Spout the numerous 
