158 PLANT LIFE 
Many of the other members of the natural 
order (Bromeliaceze) to which the pine-apple 
and the tillandsias belong, are variously 
= nag tn with respect to water supplies. 
he large bromeliad of tropical America 
possess clasping roots which fasten the short 
stem with its, relatively speaking, immense 
crown of foliage, on the branch of the tree 
which serves as its perch. The roots have little 
if anything to do with absorption, a function 
which has been almost entirely taken over 
by the tillandsia-like hairs which are found 
on the upper surfaces of the leaves. The 
latter form remarkable cisterns in which 
water is collected and stored, and from which 
it is absorbed by the hairs that are especially 
numerous where the water is stored. Each 
leaf is a long, more or less strap-shaped body, 
with the edges curving towards each other in 
the middle portion, thus forming a sort of 
gutter. Nearer the base, the leaves press 
tightly on each other and thus constitute 
the cisterns. Water falling on the upper 
surface of the leaf is directed into them by 
means of the gutter-like curvature just 
described, which causes the rain to run down 
to the centre of the crown, instead of dripping 
off as it does from most leaves. The efficient 
manner in which the foliage is arranged to 
form cisterns may be gauged by the fact that 
water plants are fairly often found growing 
and flourishing in the water thus collected 
and retained. 
