EFFECT OF ALTITUDE ON PLANTS. 
13 
they have, of course, to be content with such things as they 
can find floating in the air, as lichens blown from the branches 
of the apple-trees, bits of grass taken up by the wind. A dead 
leaf, floated by a spider’s web, I saw one take this Spring, and 
last year I saw them catching the coloured sepals of the white 
clematis which grows against the Vicarage wall. 
When I was about twelve years of age, and trapped and 
catapulted without discrimination or remorse, I must confess to 
having set a cruel trap for the Swifts, but fortunately they were 
not to be caught. I stretched a fishing line in the path of one 
of their rings from the top window at the East of the Vicarage 
to the top of the fir-tree close to the Church Tower, and on this 
line were several trout flies, fastened as droppers. But, I sup- 
pose the gut was not long enough, and the flies were too still. 
The Swifts would check and look at them, but pass on unde- 
ceived. Swallows and Sand Martins have often been unin- 
tentionally caught by fishermen on the banks of a stream, but 
then the fly is moving through the air and the deception is com- 
plete. A small feather on a small hook at the end of a fine trace 
would be very likely to catch a Swift on a windy day. 
Aubrey Edwards. 
[Since this has gone to press I have seen a notice in the 
Field , November 29, 1890, of a Swift being hooked last year on 
the Test. — A.E.] 
(To be Continued.) 
THE EFFECT OF ALTITUDE ON PLANTS. 
ROF. HENSLOW, in his most interesting paper in the 
November number of Nature Notes, asks for 
evidence as to the influence of environment upon 
plants. Without doubt, one of the most marked 
instances of the effect of conditions of climate and other external 
influences is afforded by the change which plants undergo at a 
high altitude above sea level. Many species which abound in 
the valleys are replaced on the mountain-tops by others differ- 
ing from them in ways which often suffice to stamp the latter 
as alpine at a glance. Others, ranging within specific limits 
through considerable differences of altitude, present, on the 
high mountains, varieties which never, or very rarely, occur 
on the plains. 
The nature of the changes due to altitude . — In order to obtain a 
clear idea of these changes, it will be necessary to consider 
those which are least permanent, and which occur within the 
limits of a species. Such are called forms or varieties, and 
embrace differences in the colours of the flowers, the height of 
the plant, the hairiness of the stem and leaves, the shape of the 
leaves, and so forth. We shall see that all these characters 
tend at times to become specific ; that is, characteristic of a 
species. 
