THE) TOPS OF THE: MOUNTAINS ‘189 
hairs, a convenient perching-place for small aquatic 
creatures such as the minute Crustaceans known as 
Water Fleas. Should one of these try to explore the 
bladder, the door opens easily, but closes at once 
behind the rash wanderer, imprisoning it. The 
Bladderworts do not digest the victims which they 
secure in this manner, but when the bodies are 
decomposed by means of bacteria, the products of 
decomposition are absorbed. How fatal this mouse- 
trap arrangement is to Water Fleas can be determined 
by dissecting the bladders of the plant. 
Thus far, then, as regards some of those peculiar 
members of our flora which make their living by the 
unusual method of stealing their neighbour’s goods, 
or which eke out their existence by the capture of 
animal food. Let us now take another line of 
exploration and consider the conditions which prevail 
on the loftiest portions of our islands, and how these 
affect the vegetation. Mountain-tops are always 
attractive and interesting places—the keen rarefied 
air, the freedom and openness of the summits, fill us 
with exhilaration. Our own mountains are not lofty; 
nowhere in the British Islands is a height of a mile 
attained. But we have only to ascend to a couple of 
thousand feet to note a great change in the vegetation. 
The plants of the lower grounds to a great extent die 
out (though some accompany us to our highest 
summit), and the vegetation takes on a low compact 
form, which becomes more emphasized as we ascend 
farther, till in sheltered nooks alone do we find any 
plants more than a fewinches in height. Furthermore, 
we notice an incoming of new plants unknown at 
lower levels, which search will show us to be confined 
